Butler did not participate in Wednesday's shootaround, and it is unclear at this point when he will return.
"Just a lot of pain in the joint and in the muscle around it," Butler said. "I just don't want to make it worse right now."
Butler injured his thumb Oct. 19 in a preseason game against the Charlotte Hornets and has not played since. After having an MRI on Oct. 21 that confirmed the sprain, he has had the thumb wrapped for more than a week and is still having discomfort.
"I try to come back early, and that's not always the best thing to do," Butler said. "They're just making sure when I do come back, I won't have any restraints and I'll be able to go 100 percent."
Butler's injury is a big setback for the Bulls in the short-term for two main reasons. First of all, he will not be able to guard Knicks star Carmelo Anthony on Wednesday. Secondly, Butler was in the midst of the best preseason of his career and was the best all-around player for the Bulls in the first few weeks of camp.
Coach Tom Thibodeau said he was undecided as to which player would replace Butler in the starting lineup, but the likely choice is veteran Kirk Hinrich. The combo guard started for Butler after his injury.
"Next guy get up," Thibodeau said. "We've been without Jimmy a lot, and we know what we have to do. We have a very deep team, so the next guy get in there and get it done."
After initially saying that Butler would be out two to four weeks, Thibodeau acknowledged he wasn't sure how much time his starting shooting guard would miss.
"No one knows," Thibodeau said. "Two to four, one to three, I don't know what it is. He's not comfortable going yet, so when he is, he will. We know he wants to be out there, and injuries are part of the game, so you just deal with it."
The injury comes at a bad time for Butler and the Bulls on many levels, especially given that the deadline for Butler to sign an extension with the team is Friday. If he and the organization do not come to an agreement, the 25-year-old would become a restricted free agent at the end of the season.
Butler says he is not focused on the ongoing negotiations; he's just trying to get back on the floor.
"I don't know," he said of his return from injury. "I'm hoping not too much longer. I'm hoping for Friday."