No more room for error. The Philadelphia 76ers couldn't close out the Boston Celtics at home in Game 6. Now, they're heading back up north for a Game 7 that will decide the legacies of many of the team's key figures and the future of the Sixers franchise as a whole.

The Sixers' confidence level is seemingly high heading into Sunday afternoon's matchup. They have already won twice in Boston in this series, including the most recent game when they completely owned them on their home court. Even with a bonus day of rest, the task ahead of them is not easy. The work they have put in, starting with training camp, has prepared them for a moment of this magnitude.

While anything can happen in a Game 7 setting, the Sixers need to bring their absolute best. In order to get to that level, here are five things that must happen.

5. Cycle guys in around the Big 3

Joel Embiid, James Harden and Tyrese Maxey should expect to play 40-plus minutes in the do-or-die game. The Sixers would be wise to play their best players as much as they reasonably can. Everyone else should have to prove it.

P.J. Tucker and Tobias Harris will both see plenty of minutes, but Rivers can't afford to run with them regardless. Last game, Tucker did a solid job of shooting the open shot. But his struggles to contribute in any other way besides shooting corner threes gives Boston an easy out on defense. Harris, after doing some of the dirty work while making his shots in Game 5, was a no-show outside of a few impressive takeaways.

Rivers shouldn't bench guys entirely after a bad stretch or two, but he should also be ready to toggle with the rotations as much as possible. Rivers should be able to land on a combination that works somewhere with the mix of Tucker, Harris, De'Anthony Melton, Georges Niang and one of Danuel House Jr. and Jalen McDaniels (plus Paul Reed in the few minutes of rest Embiid gets).

4. Limit Celtics' transition opportunities

Covered up by the Sixers' putrid 86 points in Game 6 is the fact that the Celtics had only 95. Embiid's spectacular defense has made life extremely hard for Boston in the half court. In this series so far, the Celtics posted a half-court offensive rating over 100 in just two of his five games. In the last two, they have been below 95.

Even though the Celtics' fast breaks are not always super efficient, the volume with which they get into them is damaging to Philly. The Sixers have to lean in one of the two directions to stop a transition attack (aside from the main one, which is to simply make shots). They must choose to either go all-in on crashing the glass to keep the ball with them or have everyone else besides the shooter get back on defense immediately.

Since their best rebounder (Embiid) is not always by the rim to clean up misses, the latter makes more sense. When the Sixers are in the half court, they should funnel guys toward Embiid at the rim and dare them to try him. But at the same time, they also need to scramble back out to the perimeter quickly to cover up the shooters.

3. Rediscover proper spacing on offense

Joe Mazzulla's decision to put Robert Williams into the starting lineup worked very well for the Celtics. He gave Boston a lob threat when they drove to the hoop and killed Philly's spacing offensively. Doc Rivers has to counter Mazzulla's decision by making a tough one: overlay Tucker's minutes with the minutes Williams sits to the best of his ability. Plugging in Melton or Niang puts a more viable shooting threat on the court, though it does either sacrifice size or defense.

Tucker will always be the guy whom the Celtics choose to roam off of. But if that roaming defender isn't Williams, the Sixers will have an easier time attacking the rim. He should still get some playing time — if Boston leans heavier into the roam and leaves him with more open space, he could end up having a strong showing on offense. But this time, he has to get his shots to fall.

Even with Boston's lineup tweak, Philly found good shots often: they just missed them. Some of their ugliest misses of the season poisoned what was, in terms of execution, not a total disaster until crunch time, which is its own problem that the Sixers must avoid. In fact…

2. Get Joel Embiid the ball

After Game 6, Embiid spelled out why the Sixers' offense fell apart in crunch time: he failed to simply get the ball. Boston got physical with him as he went to his spots and shut the typical pocket-pass window Harden uses to get it to him. Philly has to overcome that and simply get Embiid the ball.

Embiid found great success in the post in Game 5. While he shouldn't just revert back to his old tricks, the Sixers should get home more looks there. So long as Philly spaces out correctly — staying around the arc but moving around to keep the other defenders occupied — Boston would have to be more decisive about when to double. Embiid having more room to attack one-on-one should frighten the Celtics, leading to advantages in the numbers as long as Embiid makes the right pass (and his teammates find the openings).

The workload from this series is a lot for Embiid. On top of covering every attempted drive like a tarp, he has to lead the way on offense each and every possession — and all of it on a bum knee. The expectations are massive. But they come with the territory of being an MVP and someone legitimately in the conversation of best basketball player right now. A big game against the team that has always gotten the best of him can go a long way toward not just this season but his overall legacy.

The Sixers can do a lot of prep and scheme up counters for every counter the Celtics have. Their plans can come crashing down with another bad performance from one particular player.

1. James Harden must show up

One person wields a lot of power when it comes to how well the Sixers play in Game 7. While Embiid, Jayson Tatum and Jaylen Brown are obviously going to vastly impact the game, the games have gone as James Harden does. Showing up has resulted in Philly wins, while failing miserably has resulted in losses.

The most obvious thing Harden can do to help himself is to make his threes, which set up his drives. He should activate the quick hands he showed in Game 6 to make him valuable on the defensive end. Whether or not the refs are good or absolutely stink, he can't let the way they call the game throw him way off-kilter.

Harden isn't Atlas holding up the Sixers' entire world. With the MVP and enough solid three-point shooters on their side, they could still feasibly win even if Harden doesn't come with his best. What he is for Philly is its motor, revving up the offense with his command on that side of the floor. The Sixers can't expect to win the race by charging ahead like a go-kart instead of a hot rod.

Like Embiid, this game will have a massive impact on Harden's legacy. Whether he wants it to be one that overcomes his previous flameouts or the most epic one of all is up to him.