Andrew Bogut missed another match with a right hamstring issue but it didn't bother a rejuvenated Dallas as they marched to a 104-97 win over NBA champions Cleveland on Monday night.
Bogut aggravated the hamstring injury during Sunday's victory over San Antonio that previously caused him to miss six games.
Harrison Barnes scored 24 points as the Mavericks - third-last in the Western Conference but having won seven of their last 10 games - knocked off an NBA title contender for the second straight night.
Wesley Matthews had 21, and rookie point guard Yogi Ferrell scored a career-high 19 in the second game of a 10-day contract, a night after hitting two key free throws in the final seconds of a win at Southwest Division-leading San Antonio.
LeBron James had 23 points and Kyrie Irving 18 - but just one between them in the fourth quarter - for the Cavaliers, who were without fellow All-Star Kevin Love because of recurring back spasms.
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The Cavs dropped to 7-8 in January. The loss also trimmed Cleveland's lead for the top spot in the Eastern Conference to two-and-a-half games over Boston.
Dallas next step onto court on Wednesday when they face Philadelphia, who on Monday scored their latest surprising win, 122-119 over the Sacramento Kings.
Robert Covington had 23 points and 10 rebounds to rally the 76ers in a game postponed from November 30 by the NBA because of condensation on the court at the Wells Fargo Center.
Still without injured Australian No.1 draft pick Ben Simmons, the Sixers overcame 46 points from DeMarcus Cousins and won again without the also-injured centre Joel Embiid.
Embiid sat out with a left knee contusion.
Down by 16 points in the first half, the Sixers scored 42 points in the third quarter and held on when Arron Afflalo missed a tying three-point attempt at the horn.
In Boston, Isaiah Thomas scored 24 of his 41 points in the fourth quarter to help the Celtics beat Detroit 113-109 and extend their winning streak to four games.
In Miami, Goran Dragic scored 20 points and Dion Waiters added 19 as the Heat pushed the NBA's longest current winning streak to eight games with a 104-96 triumph over Brooklyn.
In Phoenix, Mike Conley scored a career-high 38 points and Memphis just missed a franchise record with 16 three-pointers as the Grizzlies rolled past the Phoenix Suns 115-96.
And in Minneapolios, Andrew Wiggins scored 27 points and Ricky Rubio made a career-high six three-pointers to lead Minnesota to a 111-105 overtime win over Orlando.
