What a 1 on 1 game is
In a 1 on 1 game you call the plays yourself, live on Court View's court, instead of letting the sim play it. Makes, misses, fouls and rebounds still come from the league's own engine; your calls decide what kind of look each trip gets. 1 on 1 is off until the commissioner turns it on, with separate switches for games against CPU-run teams and against other GMs. It works in solo leagues too (against CPU teams).
You'll find it on a Play banner near the top of the Dash and on your team's Games page, in the Start menu, and in the 1 on 1 lobby, which also lists the games live around the league.
Today's game counts
On a day your team plays, you can play that game live before the league advances (not while a sim is running). Against a CPU-run team, tap Play it live. Against a team with a GM you have to challenge them: nobody plays a human's team for them. The challenge arrives as a DM card and an urgent push, stays open for 15 minutes, and you can take it back. If they say No thanks or don't answer, the game is simmed as usual. A yes starts the game at once, and the tip waits briefly for both of you.
The result is saved at the next league sim exactly like a simmed game: stats, standings, play-by-play and injuries, playoff games included. There's no extra PP for playing it live. Every live game gets a "Live now" card in League chat, and anyone in the league can watch.
How long it takes
The league picks the length. By default the coaches play the first nine minutes of each quarter using both game plans and you call the last three, about ten minutes in all. The full format has you call every possession, about 35 minutes. On a day off you can play an exhibition against any team, home or away, in either length or with short quarters; nothing is saved, nobody gets hurt, and only you can watch.
Calling plays
On offense you call Pick & roll, Iso, Post up, Drive, Three or Motion, and can name who runs it, plus your tempo (push, even, milk) and how hard you crash the glass. On defense you call Man, Zone, Help, Trap, Press or a Double on their best scorer, plus your effort and how you handle the boards. On a pick-and-roll both sides make a blind read: the handler picks Pull up, Drive, Hit the roller or Kick out, and the defense picks Drop, Switch, Hedge, Blitz or Ice. After an offensive rebound you choose Put it back or Kick it out.
Both sides call blind and the play runs once both are in. A call into the right defense gets a better look; into the wrong one, a worse look or a turnover. No call beats everything, and the pad shows what each call stops, beats and gives up, then grades the matchup. A CPU opponent learns your habits as the game goes.
Subs, timeouts and the clock
Your coach suggests subs and you can say leave them in; in a timeout you can swap players yourself. You have your normal timeouts. Each call has a short clock (the commissioner sets it); miss it and the CPU calls for you, and miss a few in a row and your side goes on auto. The Auto button hands your side over on purpose, and any tap takes it back. If everyone leaves, the game finishes on auto. Before a scheduled advance the league waits a few minutes for games in progress, with a countdown, then finishes them on auto.
The commissioner can pause, resume or void a game (then the sim plays it), and you see a notice when they do.