Davis had a career-best 17 points and 12 rebounds, Linas Kleiza and DeMar DeRozan added 16 points apiece, and the Raptors beat the Dallas Mavericks 84-76 on Tuesday night.
Nowitzki had an MRI exam earlier Tuesday that revealed a sprained right knee and the team said he was day to day. Nowitzki, seventh in the league with 24.1 points per game, was injured in the second quarter of Monday night's 103-93 victory at Oklahoma City.
"We've got to get used to playing without the big fella for a while," said Mavericks center Tyson Chandler. "We had a tough time adjusting. Our defense held them to 84, but offensively we had nothing."
Dallas went 31 for 75 from the floor, 5 for 22 from 3-point range.
Jason Terry scored 18 points and Caron Butler 15 for the Mavericks, who had won 17 of their previous 18.
The Raptors remain without top scorer (Andrea Bargnani, 21.2 points), leading rebounder Reggie Evans (12.1), starter Sonny Weems and long-range shooter Peja Stojakovic.
Starting guard Jose Calderon became the latest addition to the Raptors' injury list when he missed the game after hurting his ankle during Monday night's 96-85 loss at Memphis. Jerryd Bayless started, then went to the locker room in the fourth quarter with an ankle problem.
Kleiza shortened the Toronto bench even further when he was ejected with 5:14 left in the third quarter after drawing his second technical foul.
Toronto, which had dropped its last 10 games in Dallas and had lost nine of its previous 11 overall, got 12 points each from Amir Johnson and Leandro Barbosa.
Dallas led in the game's first minute, but trailed the rest of the way while setting a season-low for points scored.
The Mavericks got as close as 71-68 with 7:41 left, but the Raptors answered with an 8-0 run capped by Davis' layup with 4:05 to play.
The Raptors held a 48-24 edge on points in the paint and a 42-35 rebounding advantage. Toronto had 25 fast-break points to nine for Dallas, outhustling the older Mavericks for most of the night.
"I'd credit them more than saying we gave it to 'em," said Mavericks coach Rick Carlisle, returning to the bench after missing Monday night's game after knee surgery. "I think they earned it."
Chandler's three-point play off an alley-oop dunk got the Mavericks' crowd back in the game with 5:53 left in the third quarter, pulling his team within 56-51. But the Raptors were still able to carry a 64-59 lead into the final quarter.
Dallas trailed by as many as 12 in the second quarter, but Terry's 3-pointer with 17 seconds left trimmed the deficit to 46-40 at the break.
Toronto led 23-13 after one quarter, taking advantage of seven Mavericks turnovers and Dallas' 4-for-20 shooting from the floor.
"We got off to a sluggish start, particularly defensively," Carlisle said.
Notes: Toronto opened with a lineup that featured the 6-9 Johnson as its tallest player, and Johnson has been slowed by back spasms. ... Dallas' 13-point first quarter matched its low quarter for the season. ... Davis is the son of former Maverick Terry Davis. ... Shawn Marion started at power forward in place of Nowitzki and finished with 12 points.