diff --git a/app/core/tournament/utils.ts b/app/core/tournament/utils.ts
index 53dc21493..f67b4e345 100644
--- a/app/core/tournament/utils.ts
+++ b/app/core/tournament/utils.ts
@@ -1,3 +1,4 @@
+import invariant from "tiny-invariant";
 import { Bracket } from "./bracket";
 
 export function checkInHasStarted(checkInStartTime: string) {
@@ -28,6 +29,98 @@ export function sortTeamsBySeed(seeds: string[]) {
   };
 }
 
+export function roundNamesWithDefaultBestOf(bracket: Bracket): {
+  winners: {
+    name: string;
+    bestOf: number;
+  }[];
+  losers: {
+    name: string;
+    bestOf: number;
+  }[];
+} {
+  const { winners: winnersRoundNames, losers: losersRoundNames } =
+    roundNames(bracket);
+  const { winners: winnersDefaultBestOf, losers: losersDefaultBestOf } =
+    roundDefaultBestOf(bracket);
+
+  invariant(
+    winnersRoundNames.length === winnersDefaultBestOf.length,
+    "Unexpected different length with winnersRoundNames and winnersDefaultBestOf"
+  );
+  invariant(
+    losersRoundNames.length === losersDefaultBestOf.length,
+    "Unexpected different length with losersRoundNames and losersDefaultBestOf"
+  );
+
+  return {
+    winners: winnersRoundNames.map((roundName, i) => {
+      const bestOf = winnersDefaultBestOf[i];
+      return {
+        name: roundName,
+        bestOf,
+      };
+    }),
+    losers: losersRoundNames.map((roundName, i) => {
+      const bestOf = losersDefaultBestOf[i];
+      return {
+        name: roundName,
+        bestOf,
+      };
+    }),
+  };
+}
+
+const WINNERS_DEFAULT = 5;
+const WINNERS_FIRST_TWO_DEFAULT = 3;
+const GRAND_FINALS_DEFAULT = 7;
+const LOSERS_DEFAULT = 3;
+const LOSERS_FINALS_DEFAULT = 5;
+
+function roundDefaultBestOf(bracket: Bracket): {
+  winners: number[];
+  losers: number[];
+} {
+  const { winners: winnersRoundCount, losers: losersRoundCount } =
+    countRounds(bracket);
+
+  return {
+    winners: new Array(winnersRoundCount).fill(null).map((_, i) => {
+      if (i === 0) return WINNERS_FIRST_TWO_DEFAULT;
+      if (i === 1) return WINNERS_FIRST_TWO_DEFAULT;
+      if (i === winnersRoundCount - 1) return GRAND_FINALS_DEFAULT;
+      return WINNERS_DEFAULT;
+    }),
+    losers: new Array(losersRoundCount)
+      .fill(null)
+      .map((_, i) =>
+        i === losersRoundCount - 1 ? LOSERS_FINALS_DEFAULT : LOSERS_DEFAULT
+      ),
+  };
+}
+
+function roundNames(bracket: Bracket): {
+  winners: string[];
+  losers: string[];
+} {
+  const { winners: winnersRoundCount, losers: losersRoundCount } =
+    countRounds(bracket);
+
+  return {
+    winners: new Array(winnersRoundCount).fill(null).map((_, i) => {
+      if (i === winnersRoundCount - 3) return "Winners' Semifinals";
+      if (i === winnersRoundCount - 2) return "Winners' Finals";
+      if (i === winnersRoundCount - 1) return "Grand Finals";
+      return `Winners' Round ${i + 1}`;
+    }),
+    losers: new Array(losersRoundCount)
+      .fill(null)
+      .map((_, i) =>
+        i === losersRoundCount - 1 ? "Losers' Finals" : `Losers' Round ${i + 1}`
+      ),
+  };
+}
+
 export function countRounds(bracket: Bracket): {
   winners: number;
   losers: number;
diff --git a/app/routes/to/$organization.$tournament/admin.tsx b/app/routes/to/$organization.$tournament/admin.tsx
index c80b43728..5e46d24b2 100644
--- a/app/routes/to/$organization.$tournament/admin.tsx
+++ b/app/routes/to/$organization.$tournament/admin.tsx
@@ -1,6 +1,6 @@
 import type { LinksFunction } from "remix";
+import { Outlet } from "remix";
 import { Button } from "~/components/Button";
-import { AdminTeamControls } from "~/components/tournament/AdminTeamControls";
 import styles from "~/styles/tournament-admin.css";
 
 export const links: LinksFunction = () => {
@@ -11,10 +11,12 @@ export default function AdminPage() {
   return (
     <>
       <div className="tournament__admin__buttons-container">
+        {/* Don't show when check in is not concluded + secure route */}
         <Button>Start tournament</Button>
+        {/* TODO: */}
         <Button variant="outlined">Edit tournament</Button>
       </div>
-      <AdminTeamControls />
+      <Outlet />
     </>
   );
 }
diff --git a/app/routes/to/$organization.$tournament/admin/index.tsx b/app/routes/to/$organization.$tournament/admin/index.tsx
new file mode 100644
index 000000000..2382ac0b3
--- /dev/null
+++ b/app/routes/to/$organization.$tournament/admin/index.tsx
@@ -0,0 +1,262 @@
+import {
+  closestCenter,
+  DndContext,
+  KeyboardSensor,
+  PointerSensor,
+  useSensor,
+  useSensors,
+} from "@dnd-kit/core";
+import {
+  arrayMove,
+  SortableContext,
+  sortableKeyboardCoordinates,
+  useSortable,
+  verticalListSortingStrategy,
+} from "@dnd-kit/sortable";
+import { CSS } from "@dnd-kit/utilities";
+import classNames from "classnames";
+import * as React from "react";
+import { useFetcher, useMatches } from "remix";
+import { Alert } from "~/components/Alert";
+import { Button } from "~/components/Button";
+import { TOURNAMENT_TEAM_ROSTER_MIN_SIZE } from "~/constants";
+import { checkInHasStarted } from "~/core/tournament/utils";
+import type { FindTournamentByNameForUrlI } from "~/services/tournament";
+import type { Unpacked } from "~/utils";
+import { useTimeoutState } from "~/utils/hooks";
+
+// TODO: https://docs.dndkit.com/presets/sortable#drag-overlay
+// TODO: what if returns error? check other APIs too -> add Cypress test
+export default function AdminDefaultTab() {
+  const seedsFetcher = useFetcher();
+  const [, parentRoute] = useMatches();
+  const { id, teams, checkInStartTime } =
+    parentRoute.data as FindTournamentByNameForUrlI;
+  const [teamOrder, setTeamOrder] = React.useState(teams.map((t) => t.id));
+  const sensors = useSensors(
+    useSensor(PointerSensor),
+    useSensor(KeyboardSensor, {
+      coordinateGetter: sortableKeyboardCoordinates,
+    })
+  );
+
+  const teamsSorted = teams.sort(
+    (a, b) => teamOrder.indexOf(a.id) - teamOrder.indexOf(b.id)
+  );
+
+  return (
+    <>
+      <SeedAlert
+        fetcher={seedsFetcher}
+        tournamentId={id}
+        teamOrder={teamOrder}
+      />
+      <ul>
+        <li className="tournament__admin__teams-list-row">
+          <div className="tournament__admin__teams-container__header">Seed</div>
+          <div className="tournament__admin__teams-container__header">Name</div>
+          <div className="tournament__admin__teams-container__header">
+            {checkInHasStarted(checkInStartTime) ? "" : "Registered at"}
+          </div>
+          <div className="tournament__admin__teams-container__header">
+            Roster size
+          </div>
+        </li>
+        <DndContext
+          id="team-seed-sorter"
+          sensors={sensors}
+          collisionDetection={closestCenter}
+          onDragStart={() => null}
+          onDragEnd={(event) => {
+            const { active, over } = event;
+
+            if (!over) return;
+            if (active.id !== over.id) {
+              setTeamOrder((teamIds) => {
+                const oldIndex = teamIds.indexOf(active.id);
+                const newIndex = teamIds.indexOf(over.id);
+
+                return arrayMove(teamIds, oldIndex, newIndex);
+              });
+            }
+          }}
+        >
+          <SortableContext
+            items={teamOrder}
+            strategy={verticalListSortingStrategy}
+          >
+            {teamsSorted.map((team, i) => (
+              <SortableRow
+                key={team.id}
+                team={team}
+                seed={i + 1}
+                disabled={seedsFetcher.state !== "idle"}
+              />
+            ))}
+          </SortableContext>
+        </DndContext>
+      </ul>
+    </>
+  );
+}
+
+function SeedAlert({
+  tournamentId,
+  teamOrder,
+  fetcher,
+}: {
+  tournamentId: string;
+  teamOrder: string[];
+  fetcher: ReturnType<typeof useFetcher>;
+}) {
+  const [teamOrderInDb, setTeamOrderInDb] = React.useState(teamOrder);
+  const [showSuccess, setShowSuccess] = useTimeoutState(false);
+
+  React.useEffect(() => {
+    // TODO: what if error?
+    if (fetcher.state !== "loading") return;
+
+    setTeamOrderInDb(teamOrder);
+    setShowSuccess(true, { timeout: 3000 });
+  }, [fetcher.state]);
+
+  const teamOrderChanged = teamOrder.some((id, i) => id !== teamOrderInDb[i]);
+
+  return (
+    <fetcher.Form
+      action={`/api/tournament/${tournamentId}/seeds`}
+      method="post"
+      className="tournament__admin__form"
+    >
+      <input type="hidden" name="seeds" value={JSON.stringify(teamOrder)} />
+      <Alert
+        type={teamOrderChanged ? "warning" : showSuccess ? "success" : "info"}
+        className="tournament__admin__alert"
+        rightAction={
+          <Button
+            className={classNames("tournament__admin__alert__button", {
+              hidden: !teamOrderChanged,
+            })}
+            type="submit"
+            loadingText="Saving..."
+            loading={fetcher.state !== "idle"}
+          >
+            Save seeds
+          </Button>
+        }
+      >
+        {teamOrderChanged ? (
+          <>You have unchanged changes to seeding</>
+        ) : showSuccess ? (
+          <>Seeds saved successfully!</>
+        ) : (
+          <>Drag teams to adjust their seeding</>
+        )}
+      </Alert>
+    </fetcher.Form>
+  );
+}
+
+function SortableRow({
+  team,
+  seed,
+  disabled,
+}: {
+  team: Unpacked<FindTournamentByNameForUrlI["teams"]>;
+  seed: number;
+  disabled: boolean;
+}) {
+  const [, parentRoute] = useMatches();
+  const { checkInStartTime } = parentRoute.data as FindTournamentByNameForUrlI;
+
+  const { attributes, listeners, setNodeRef, transform, transition } =
+    useSortable({ id: team.id, disabled });
+
+  const style = {
+    transform: CSS.Transform.toString(transform),
+    transition,
+  };
+
+  return (
+    <li
+      className={classNames("tournament__admin__teams-list-row", "sortable", {
+        disabled,
+      })}
+      ref={setNodeRef}
+      style={style}
+      {...attributes}
+      {...listeners}
+    >
+      <div>{seed}</div>
+      <div>{team.name}</div>
+      <div>
+        {!checkInHasStarted(checkInStartTime) ? (
+          <>
+            {new Date(team.createdAt).toLocaleString("en-US", {
+              month: "numeric",
+              day: "numeric",
+              hour: "numeric",
+              minute: "numeric",
+            })}
+          </>
+        ) : team.checkedInTime ? (
+          <CheckOutButton teamId={team.id} />
+        ) : team.members.length >= TOURNAMENT_TEAM_ROSTER_MIN_SIZE ? (
+          <CheckInButton teamId={team.id} />
+        ) : null}
+      </div>
+      <div
+        className={classNames({
+          tournament__admin__ok:
+            team.members.length >= TOURNAMENT_TEAM_ROSTER_MIN_SIZE,
+          tournament__admin__problem:
+            team.members.length < TOURNAMENT_TEAM_ROSTER_MIN_SIZE,
+        })}
+      >
+        {team.members.length}
+      </div>
+    </li>
+  );
+}
+
+function CheckOutButton({ teamId }: { teamId: string }) {
+  const fetcher = useFetcher();
+  return (
+    <fetcher.Form
+      method="post"
+      action={`/api/tournamentTeam/${teamId}/check-out`}
+      className="tournament__action-section__button-container"
+    >
+      <Button
+        tiny
+        variant="minimal-destructive"
+        loading={fetcher.state !== "idle"}
+        loadingText="Checking out"
+        type="submit"
+      >
+        Check-out
+      </Button>
+    </fetcher.Form>
+  );
+}
+
+function CheckInButton({ teamId }: { teamId: string }) {
+  const fetcher = useFetcher();
+  return (
+    <fetcher.Form
+      method="post"
+      action={`/api/tournamentTeam/${teamId}/check-in`}
+      className="tournament__action-section__button-container"
+    >
+      <Button
+        tiny
+        variant="minimal"
+        loading={fetcher.state !== "idle"}
+        loadingText="Checking in"
+        type="submit"
+      >
+        Check-in
+      </Button>
+    </fetcher.Form>
+  );
+}
diff --git a/app/routes/to/$organization.$tournament/admin/start.tsx b/app/routes/to/$organization.$tournament/admin/start.tsx
new file mode 100644
index 000000000..bcec6a0b6
--- /dev/null
+++ b/app/routes/to/$organization.$tournament/admin/start.tsx
@@ -0,0 +1,23 @@
+import { useMatches } from "remix";
+import { eliminationBracket } from "~/core/tournament/bracket";
+import { roundNamesWithDefaultBestOf } from "~/core/tournament/utils";
+import type { FindTournamentByNameForUrlI } from "~/services/tournament";
+
+export default function StartTournamentPage() {
+  const [, parentRoute] = useMatches();
+  const { teams } = parentRoute.data as FindTournamentByNameForUrlI;
+
+  const teamCount = teams.reduce(
+    (acc, cur) => acc + (cur.checkedInTime ? 1 : 0),
+    0
+  );
+  return (
+    <pre>
+      {JSON.stringify(
+        roundNamesWithDefaultBestOf(eliminationBracket(teamCount, "DE")),
+        null,
+        2
+      )}
+    </pre>
+  );
+}
diff --git a/prisma/seed/script.ts b/prisma/seed/script.ts
index 7b5e039f0..7092c446a 100644
--- a/prisma/seed/script.ts
+++ b/prisma/seed/script.ts
@@ -165,14 +165,16 @@ export async function seed(variation?: "check-in") {
     }
 
     for (const [mockTeamI, mockTeam] of mockTeams.entries()) {
+      const memberCount = (mockTeamI % 5) + 2;
       const team = await prisma.tournamentTeam.create({
         data: {
           name: mockTeam,
           tournamentId,
+          checkedInTime: memberCount >= 4 ? new Date() : undefined,
         },
       });
 
-      for (let memberI = 0; memberI < (mockTeamI % 5) + 2; memberI++) {
+      for (let memberI = 0; memberI < memberCount; memberI++) {
         const memberId = userIdsCopy.shift()!;
         await prisma.tournamentTeamMember.create({
           data: {