CLEVELAND -- The only thing that finally slowed down Jimmy Butler late Monday night was a headache.

He had just played 44 minutes, scoring 20 points, including nine of his team's last 15 in the fourth quarter, to go along with six assists, five rebounds and three steals in the Chicago Bulls' 99-92 victory over the Cleveland Cavaliers in Game 1 of their semifinal playoff series.

Oh, and he ran up and down the floor defending the best player in the world.

"Can I get an Advil or something?" Butler said.

Butler's pain was surely eased by the fact that he had just capped off one of his best and most important games as a pro. He more than held his own against LeBron James, who finished with 19 points on 9-of-22 shooting. Butler carried his team offensively down the stretch and made plays when needed most.

As usual, Butler played without fear.

"I feel like we're both two NBA players," Butler said of James. "His name might be more well-known than mine, but I'm just here to compete. I'm here to play. Everybody knows that LeBron is a hell of a player, I'm not knocking that. But I think I'm a decent player. I think I can hang with the best of them."

"I feel like we're both two NBA players. His name might be more well known than mine, but I'm just here to compete. I'm here to play. Everybody knows that LeBron is a hell of a player, I'm not knocking that. But I think I'm a decent player. I think I can hang with the best of them." Jimmy Butler

That confidence has been there in Butler's game all season. He has ascended from a defensive-minded swingman with a questionable jumper to an All-Star and one of the game's best two-way players. But what he showed throughout the Bulls' first-round series win against the Milwaukee Bucks, and again in Game 1 against James and the Cavs, is that he's ready to take another step toward superstardom.

All-Stars make big plays in games. Superstars hold James to 19 points and continue hitting big shots down the stretch in playoff games.

"He's just playing with a lot of confidence," Bulls forward Taj Gibson said. "He just took the task of trying to guard LeBron, just trying to slow him down. And the bright side is that he knew he had guys behind him that's talking to him and helping him, showing bodies, and when that happens, he can just focus on his offense. Right now he's just focusing on his defense, letting the game come to him and you can see."

Butler has become the complementary piece the Bulls have been trying to pair Derrick Rose with for years. The difference is that Butler plays like he isn't deferring to anyone. He plays like a player who knows his time has come to show what he can do.

"He's definitely not backing down, that's not who he is," Bulls center Joakim Noah said. "He hasn't since he's been in the league, so that hasn't changed one bit. He's just a more experienced and better basketball player. ... He's been playing at a high level for a while now. I love his competitive spirit. He's bringing it."

Butler's spirit has helped spark an already confident Bulls team as it tries to get past James in the playoffs for the first time. Butler is setting a defensive tone that the rest of his teammates are following. He knows they have his back, but he doesn't need them nearly as much anymore. No one stops James completely, but Butler's game has elevated to a point where he can slow James down better than almost anyone in the league.

"I think I did well, made him work for everything," Butler said of his defensive performance on James. "But I think my teammates did a great job of contesting his shots at the rim. And just making him work hard for every basket, every rebound and every assist that he got."

Butler put in most of the work, though. In a series in which containing James is paramount, Butler did his job on Monday night. He also scored 20 points in the process -- because that's what superstars do.