Young had been one of three Sixers to start all 41 games this season until Friday. He scored 16 of his 22 points in the second quarter to help the Sixers grab an early double-digit lead and beat the second-best team in the West.
"If we're winning, I'm fine. If we're losing, then I'm unhappy," Young said. "Very unhappy."
He'll have to get used to coming off the bench. Coach Eddie Jordan said he's sticking with his lineup and treating the final 10 games before the All-Star break like a mini-playoff.
Williams came off the bench for only the third time this season and scored 11 points. Young and Williams were the only Sixers in double figures entering the fourth quarter.
Maybe Jordan is on to something as the 14-win Sixers still believe they have a shot at the eighth playoff seed in the East.
"They came in and turned the game around for us and kept it going," Jordan said.
Marion needed three stitches, said he "hurt like hell," but will keep playing.
It seemed inevitable that the Mavericks would eventually make a run at the Sixers and send Philadelphia to another close, crushing loss. After all, the Sixers had blown so many large leads late in defeat. Not on this night.
The Sixers kept running, pushing and scoring. Marreese Speights, who scored 14 points, made the first three baskets of the fourth for a 78-67 lead. Willie Green's three-point play off a driving layup pushed the lead to 14.
Nowitzki buried an 18-footer that pulled the Mavericks within single digits. Allen Iverson, voted to start in the All-Star game Thursday, scored a twisting layup and made a free throw and the lead was back to 12.
That was good enough for the Sixers to hold on and win only their seventh home game of the season.
Nowitzki scored 15 points and Drew Gooden had 14 for Dallas.
"We had lapses at the wrong time," said Mavericks coach Rick Carlisle. "They're a talented team, certainly better than their record."
Jordan said before the game Brand was close to a return to the starting lineup after his unceremonious benching six weeks ago. Jordan kept quiet that Brand was actually in the starting lineup. Brand and Holiday scored Philadelphia's first eight points of the game to make the lineup move seem like a small success.
"I figured I've been playing well, well enough to start," Brand said. "What we were doing was OK, but it wasn't working as well as we wished it would. Now it's a new shakeup."
Young, the 6-foot-8, 220-pound power forward, was the one who made it a smashing one. Young was 6 of 8, made two 3-pointers and scored 16 points in the second quarter as the Sixers outscored Dallas by 13.
Williams hit a little floater and Young followed with a 3 to help the Sixers grab a 54-48 lead at halftime.
"Everything they did, every single shot went in during the second quarter," a frustrated Marion said.
Young finished 9 of 12 from the floor and provided the energy and scoring off the bench the Sixers have missed all season.
"That was just me going out there and playing my game and not worrying about everything else," Young said.
76ers center Sam Dalembert is planning another visit to Haiti to aid the relief effort. Dalembert, the NBA's only Haitian-born player, was there on a two-day, goodwill mission earlier this week and said he hoped to return to Haiti over the All-Star break. ... Jordan was glad Iverson was voted an Eastern Conference All-Star starter. "The fans remember him as an exciting player and he's certainly added another dimension for us," Jordan said. "He's very popular, that's what the voting is for." ... Phillies All-Star center fielder Shane Victorino, who finalized a $22 million, three-year contract earlier in the day, attended the game.