Sixers into playoffs after Cavs down Nets
Mitchell made 10-of-22 from the field including five three-pointers while Caris LeVert added 18 from the bench against his former club as Cleveland improved to 46-28 to tighten their grip on fourth in the Eastern Conference.
Cleveland's victory ensured that third-placed Philadelphia became the latest team to punch their ticket to the playoffs despite not playing on Tuesday.
While Cleveland are yet to clinch, it will take a monumental collapse in the final weeks of the season for them not to advance to the postseason.
Tuesday's game could well turn out to be a sneak preview for the playoffs, with Brooklyn still occupying the sixth automatic qualifying spot in the Eastern Conference.
Against Cleveland they started brightly, taking a 30-23 lead into the second quarter before being outscored 71-48 in the next two periods to effectively cede the game, even if they managed to reduce the deficit to single digits in the final stages.
Day'Ron Sharpe led Brooklyn's scoring with 20 points while Spencer Dinwiddie had 19 points with 11 assists and five rebounds.
Cavs coach J.B. Bickerstaff was unhappy that his team eased off late in the fourth quarter.
"We need to play a complete game," Bickerstaff said.
"We allowed the lead to dictate our emotions, we allowed a big play to dictate our emotions, instead of doing the job and finishing the game the way we need to finish the game," Bickerstaff added.
Nets coach Jacques Vaughn lamented his team's collapse in the second and third quarters.
"That's a big question for us," Vaughn said. "I think we got a little stagnant with the basketball. Tough second quarter for us.
"Along those lines of putting four quarters together, it all seems as if there's one quarter that punches us in the gut a little bit."
Elsewhere Tuesday, the Los Angeles Clippers' stumbled to a 101-100 defeat to the Oklahoma City Thunder in a game that saw Clippers ace Paul George exit with an apparent right leg injury in the fourth quarter.
George needed to be carried back to the locker room after his right knee buckled in a collision with the Thunder's Lu Dort in the fourth quarter.
There was no immediate word on the extent of George's injury, with Clippers coach saying the eight-time All-Star was still being evaluated.
Boston topple soaring Kings
In Sacramento, the Boston Celtics' gave the high-flying Kings a postseason reality check with a blowout 132-109 win.
Sacramento have been one of the surprise packages of the Western Conference this season, sitting third in the standings.
But the Kings were overpowered by a Celtics line-up that showed flashes of their dominant early season form as they cut loose in the second half to outscore Sacramento 72-55.
Jayson Tatum led the Celtics scoring with 36 points while Jaylen Brown added 27 points and Derrick White 20.
In other games on Tuesday, Trae Young finished with 30 points in Atlanta's 129-107 win over the lowly Detroit Pistons, who are propping up the East with a league-worst record of 16-57.
Atlanta improved to 36-36 with the victory and are on track for at least a spot in the play-in tournament.
In Orlando, Gary Harris finished with 22 points and Franz Wagner 20 as the Magic dented Washington's playoff aspirations with a 122-112 victory.
The Wizards are currently outside the play-in places in 12th spot in the East with a 32-40 record.