Larry Bird said it all the time: Game 5 is the most important game of any playoff series.

And for the Celtics, tonight’s Game 5 is a Must Win. It will be an awfully tall order to win this series if they lose tonight. I don’t see them winning Game 6 at the Garden then a deciding seventh game in Atlanta on Saturday. That’s just asking much too much.

The Celtics were a different team at home in Game 3 and Game 4 than they were down in Atlanta. They played well right out of the gate, they rebounded the ball, and received contributions from different players. Isaiah Thomas found his groove as the Celtics made adjustments to free him up.

Speaking of adjustments, Brad Stevens showed why he is so highly regarded as a coach. He knew things had to change. In Atlanta the Celtics got behind early and were never in a rhythm. He benched Jared Sullinger and put in Jonas Jerebko and that paid immediate dividends. Jerebko finished with a double double in both games at the Garden.

In Game 4, Paul Millsap turned into a scoring machine. Stevens made the key in game adjustment putting Marcus Smart on Millsap. Smart shut down the Hawks All-Star and the Celtics went on to grab the overtime win.

But it will be different in Game 5. The Hawks will have their crowd behind them at Philips Arena. Historically in the playoffs, home teams win 64 percent of the time. Mike Budenholzer is a very good coach, and in the chess match with Stevens, it’s his turn to make the key adjustments.

Millsap was quiet in the first three games scoring a total of 26 points. He had 45 in game four. The Celtics need to do a better job on him tonight.

The Celtics cannot rely too much on Thomas. That’s playing right into the Hawks’ hand. They need Jerebko, Evan Turner, Marcus Smart, and Jae Crowder to make big time contributions. If tonight is just the Isaiah show, the Celtics will not win.

Lastly, the Celtics need to contain Jeff Teague. When he gets going  –shooting three’s and penetrating and dishing to their shooters — the Hawks become a plus offensive team. The Celtics need to pressure Teague and take him out of his rhythm.

Can the Celtics win tonight? Sure they can. But it will not be easy. They have yet to win an away playoff game under Stevens. Tonight would be a great time to get one.