It's hard to tell what's most impressive about Jimmy Butler's stretch of success during the Chicago Bulls' impressive playoff run.

Perhaps it's the fact that the second-year swingman, who only started 20 games during the regular season, has effectively contained Joe Johnson, Deron Williams and LeBron James. Or maybe it's that, while guarding James in Game 1 of the Eastern Conference semifinals, Butler managed to post 21 points and a game-high 14 rebounds.

Or maybe, and this is most likely, it's that Butler has played every second of Chicago's past three playoff games. The 23-year-old Butler was just the fourth player in league history to pull off that feat. According to the NBA, only Moses Malone (1981), Nick Van Exel (1995) and Allen Iverson (2005) had done that before. Not bad company.

Butler's "complete game" run will likely end soon. But if the Bulls want to maintain any hope of knocking off the heavily favored Heat, they'll need Butler's excellent defense on James to continue.

"[Butler's] a tough kid," Tom Thibodeau, the always-understated Bulls coach, said about Butler's impressive streak. "He's mentally tough, and that's what we need him to do right now."

Butler isn't the first Bulls player to put in extreme minutes this year. Forward Luol Deng averaged nearly 39 minutes during the regular season, leading the NBA. But Deng, who normally guards James when the Bulls play the Heat, has been hospitalized during the past week after a spinal tap procedure. And Butler has filled in wonderfully.

Butler held James to two points in the first half of Monday's game, the four-time MVP's lowest single half scoring output of his playoff career. This after guarding Johnson and Williams in a grueling Game 7 in Brooklyn on Saturday.

"Jimmy is really turning into a very good NBA player here early in his career," Dwayne Wade said. "His confidence level is very high, and they believe in him. He's not only knocking down shots, he's getting to the paint. Rebounding the ball, he's down there. He's guarding big guys. He's guarded LeBron in the post, in the paint. He's got good height. He's a solid player. I think he's probably better than a lot of people thought he was going to be this early in his career."

Butler has greatly benefited from playing in Thibodeau's brilliant defensive system, and it certainly helps to have defensive stalwart Joakim Noah playing behind him. But guarding James is the hardest task imaginable for an NBA defender, and Butler is doing it while logging his first significant postseason minutes (he played a total of four minutes in the 2012 playoffs).

Before Monday's game, Butler called Deng to ask for advice on guarding James.

"Take up (James') space," Deng said, "make everything tough for him, challenge every shot."

Butler, who earned the nickname "Kobe stopper" for an impressive performance against Bryant earlier this year, refused to take much praise for his job on James.

"That caliber of a player, there's no really stopping him," Butler said of James. "It's all about containment. And I felt like myself and all my teammates, we tried to make everything tough for him. I felt like that was the key."