CHICAGO -- Boston Celtics coach Doc Rivers said Tuesday he's impressed with the job Chicago Bulls coach Tom Thibodeau is doing this season despite facing some adversities, especially being without Derrick Rose as he recovers from ACL surgery.

Thibodeau, who was the Celtics' associate head coach under Rivers for three seasons, has had to deal with losing Rose, injuries to Kirk Hinrich and Rip Hamilton, and a makeover of the team's bench. The Bulls are currently 13-10 and have won five of their previous seven games heading into Tuesday's meeting with the Celtics.

"I think he does a great job every year," Rivers said prior to the Celtics' shootaround at the Moody Bible Institute. “I don't know if it is one year. I think since he's been here he's been fantastic.

"You think about this year, forget they lost Rose, that's one thing, then they lost a lot of players from last year's team that had a lot to do with why they were winning. A lot of them were significant role players that their numbers don't show up, but they did a lot of things. And then they bring in a lot of new guys. That's a lot on his plate."

Rivers believes this season has tested Thibodeau and provided him another learning experience as a head coach.

"I think you learn every year," said Rivers, whose team is 12-11. “I think this is another one. I think what he probably learned is you try to keep as many core guys as you can on a team instead of mixing it up, which would be my guess. But the other part is, yeah, you figure it out. As coaches, you get that. Thibs was ready for that. He worked all summer to get ready for this."

Since last playing the Celtics in the seventh game of the season, the Bulls have improved. Rivers said he didn't think the Bulls were getting more accustomed to playing without Rose, but rather they were simply improving.

"I don't think the Rose factor for Chicago has a lot of impact on how they play," Rivers said. “I've always found if you have training camp without the guy, see that part is gone. You come into the season understanding you don't have the guy; you just play with what you have. I think just they're playing better. I don't think the Rose factor has anything to do it."

Rivers said the Bulls' defense has had a lot to do with their recent success. Rivers still talks often with Thibodeau, and Rivers knew the Bulls' defense hadn't been living up to Thibodeau's standards.

"I know early into the season, Thibs was frustrated with their ability to defend, but now I think they're terrific," Rivers said. “They're back to what they were.

"You take Paul [Pierce] away from our team, and our ability to score goes away a little bit. And the way you'd have to stay in the games would be with your defense. That's what they're doing. They've won a lot of games where they've hung around and won them at the end because that's who they have to be right now."