"For one, they were already having a successful season," Butler said, explaining his reasons for joining Chicago. "They had some interest in me before, over the summer, and things of that nature. And once I talked to the GM Gar Forman and Coach [Tom] Thibodeau, I just felt that this would be the best fit for me."
Butler was bought out by the Los Angeles Clippers late Sunday night and cleared waivers on Wednesday.
The Bulls don't intend for Butler or any new player to break into the starting lineup or even log major minutes, a source told ESPNChicago.com's Nick Friedell.
"[Thibodeau] told me that I needed to come in and practice really hard, work hard, and just kind of stay ready right now, because they already have their rotation set and they're having a successful season right now and the guys in the rotation have done a good job for him," Butler said. "He told me just to come in, work hard, get acclimated with the system and just stay ready for when my opportunity comes along."
Butler averaged five points in 18 minutes per game this season after averaging 11.9 points last season. A 6-foot-7 swingman, Butler, 31, has averaged 8.6 points per game in eight NBA seasons.
"I'm a good individual defender, a good team defender," Butler said. "Shooting the ball is my skill that I bring. That's the one thing that I'm known for is being able to shoot the ball. A catch-and-shoot guy, one or two dribble pull-up guy. Just a smart, cerebral basketball player. Not going to make too many mistakes. A team player."
Butler said he's looking forward to playing with Derrick Rose.
"I look forward to it," he said. "He's arguably the best point guard in the game, as well as the best player this year -- MVP caliber player. Puts a ton of pressure on the defense. Always in the paint at the front of the rim, making plays for guys finishing.
"So I'm really excited to play with him because he gets so much attention that when I have the opportunity to get on the floor it's a lot of good looks, a lot of open shots that he creates for people."
Terms of the deal were not disclosed.