If the Celtics hope to escape a 2-0 hole against the Bulls and avoid a third straight first-round ouster, it's going to come down to one man. No, not Isaiah Thomas. Head coach Brad Stevens. Stevens has lived a charmed existence since arriving in Boston and overseeing a transformation from 25 wins three years ago to 53 victories this year. Along the way, he has faced pretty much zero criticism, because his team keeps wildly exceeding expectations, first simply by making the playoffs, then by challenging for a top-three seed, and then by racing to this improbable No. 1 seed. But that lengthy honeymoon is finally over. The Celtics not only trail the eighth-seeded Bulls with the action returning to Chicago, they've been embarrassed. The Bulls manhandled them in a close Game 1 victory that exposed their soft underbelly. They were then humiliated in Tuesday's 111-97 Game 2 loss that puts the bullseye squarely between Stevens' unflappable, expressionless eyes. The coach has cracked the code when it comes to winning over the course of 82 games. The question is what happens when the season condenses to a series of seven-game encounters and the rules change. So far he has come up empty. Those open shots Isaiah Thomas nailed while becoming the King in the Fourth? They're swallowed up by constant double teams. The free-flowing rotation that often left the second unit indistinguishable from the first? Say buh-bye. Benches shorten in the playoffs for a reason. The Give-It-To-Whoever's-Open egalitarian offensive ethos? It works better when sphincters aren't slammed shut like United's armored flight deck.