The 31-year-old Wallace wasn't pleased with the Celtics losing six of their past seven and was eager to help the team get things headed in the right direction.
"I could sense that he was going to be focused and ready," Stevens said. "He's such a competitive guy."
Wallace led a productive night for Boston's reserves with a season-high 17 points, Jordan Crawford had 21 points and the Celtics defeated the Charlotte Bobcats 96-86 Monday night for their second straight victory since ending a six-game losing streak.
"I had a talk with coach and the main thing he wanted me to do was to play the way I know how to play," Wallace said. "He told me not to try to figure out how to fit in or what to do, just go out and play basketball the way I know how to play basketball. ... I just wanted to go out there and be aggressive and play the way I know how to play."
Said Stevens: "The effort was good and [Wallace] was a big part of that. He's contagious in the way he plays. When he plays like that, it makes it easier to follow. We're kind of finding our way back to that Jeff [Green] and Gerald lineup more and more."
For most of the game he looked like the Wallace of old, spinning and twisting his way to the basket, getting good shots and drawing contact.
Crawford said Wallace gives the team "everything we need" to be successful.
"He can check the best player, he can rebound, he can pass and he can score," Crawford said.
Boston's reserves outscored Charlotte's bench players 39-15.
"The bench play was the difference in the game," Bobcats coach Steve Clifford said.
Crawford was 5 of 11 from the field and had five assists as the Celtics avenged an 89-83 loss to the Bobcats on Nov. 13. Wallace, who played for the Bobcats from 2004-11, was 6 of 10 from the field.
Charlotte cut Boston's lead to 68-66 entering the fourth quarter, but the Celtics got a 3-pointer from Lee and a layup by Kris Humphries off a pick and roll to score 10 straight points.
The Bobcats would trim the lead to six with 1:25 remaining in the game before the Celtics got an offensive rebound off a missed shot and Crawford hit a pair of free throws to make it a three-possession game with 34 seconds remaining.
The Celtics came in looking to avenge a loss two weeks ago to the Bobcats that started their six-game losing skid.
Boston started slow Wednesday, falling behind 20-10 but took a 47-38 lead into halftime after outscoring the Bobcats 33-17 in the second quarter. The Celtics came alive behind the outside shooting of Crawford, who knocked down three 3-pointers and led all scorers at the break with 12 points and strong play from the bench.
"We came out the start of the second quarter and had nothing," Clifford said. "The same thing happened at the start of the fourth."
Charlotte's struggles continue at home, where they have lost five of their last six.
The Bobcats entered the game with the NBA's third best defense, allowing just 83.6 points on 38 percent shooting. But in their last six home games they have surrendered 98 points per game on 48 percent shooting.
"I don't know what it is right now with us being at home, but we just don't have that energy like we have on the road," said Bobcats center Al Jefferson. "That's unheard of for me. I'm always used to playing well at home and not good on the road, but it is vice versa here."
Henderson has scored in double digits 13 times this season, including the last six games. ... Green has scored in double digits 13 times for the Celtics. ... The Celtics are 2-3 against the Bobcats in their last five games. ... Bismack Biyombo, who recently received a contract extension from the Bobcats, has not played in two of the team's last three games. ... The Bobcats had 17 turnovers to Boston's 12.