"We got lazy," Oklahoma City's Russell Westbrook said. "We were up and we kind of calmed down while they kept fighting."
The Thunder lost for the first time in four games this season without Durant, the NBA's leading scorer at 27.3 points per game. Durant missed his second straight game with a sprained left knee.
"That's 30 points a night," guard James Harden said. "We're capable of winning without him but we have to get stops. It's that much more pressure on us to get stops. We were ready for it, we just didn't do it."
The Thunder beat the Nets 123-120 in three overtimes on Wednesday night in New Jersey but couldn't pull off another one without the NBA's reigning scoring king.
Coach Scott Brooks said Durant's knee is improving, and he could return Sunday when the Thunder host the Golden State Warriors.
"Hopefully he gets better quickly and comes back Sunday," Brooks said. "We'll see how he feels and evaluate him before the game."
Westbrook scored 38 points Wednesday but was held to 20 points in this one, making 9-of-19 shots.
Already without Durant, the Thunder lost forward D.J. White in the second to a sprained right ankle. White was in a walking boot after the game.
"We'll see how he feels after the plane ride home," Brooks said.
Johnson made two free throws to put Toronto up 105-91 with 2:33 left, but the Thunder cut it to nine on a jumper by Byron Mullens and a free throw and a layup from Thabo Sefolosha.
Bargnani stopped the run with a jump shot and then added another jumper before Barbosa stole the ball at midcourt and raced in for a layup, making it 111-96.
Toronto led 28-25 after one but Oklahoma City closed the second quarter with a 7-2 surge to carry a 59-52 edge into the break. Bargnani scored 10 points in the first half, all in the first quarter.
The Raptors reclaimed the lead with a 17-4 run to begin the third, including six points from Bargnani and huge dunks by Johnson and Weems.
"The start of the third quarter is where we lost it," Green said. "They scored 34 points in the third quarter and that can't happen. You can't win ballgames like that. That's something we've got to correct."
The Thunder made just 6-of-21 field-goal attempts in the third and were outscored 34-18 as Toronto took an 86-77 lead into the fourth.
Raptors forward Peja Stojakovic missed his third straight game with a sore left knee. ... Calderon's career high in assists is 19, set March 29, 2009. ... Westbrook has topped 20 points in five straight games. ... The Raptors have shot 50 percent or better from the field in consecutive games for the first time this season.