The Sixers were dealt an early blow when Young limped off the court with 2:15 left in the first quarter. Young landed on Smith's foot and stayed on the court for a few minutes writhing in pain.
"At this time of the season, we can't afford injuries," Sixers coach Tony DiLeo said. "Hopefully, Thad will get back soon."
Young, who had played in every game this season, scored six points before the injury. He entered the game averaging 15.3 points. X-rays were negative and Young's status for Thursday's game against Milwaukee is not immediately known. He is scheduled for an MRI on Wednesday.
"It looked bad because he really couldn't walk off the court," Miller said. "It could be a couple of weeks. I don't know. He's been playing good ball for us. Other guys have to keep stepping up."
Take Speights, for instance.
The 6-foot-10 rookie from the University of Florida played 25 minutes and shot 6-of-13 from the field.
"Any time my name is called, I'm ready to go in," Speights said. "My job is to come in and do whatever they need me to do."
After ascending to 37-33 last week, their best record in four years, the Sixers dropped two straight before this win.
"It was important to get this win," Iguodala said. "Everybody chipped in for us to get that win."
Smith was sensational with an array of jumpers, 3-pointers and several rim-rattling dunks. The 6-foot-9 forward was 13-of-15 from the field while hitting all three of his 3-pointers.
"It was just a game where I was feeling it," Smith said. "I didn't force anything and let it come to me. Players have games like this in the league and this was just my night."
Flip Murray added 19 and Joe Johnson had 11 for the Hawks (43-32), who haven't won a road game over a team currently in playoff position since a victory on Feb. 11 at Detroit. Still, Atlanta holds the No. 4 spot in the postseason.
"We still have a lot of games left to play," Atlanta coach Mike Woodson said. "We just have got to keep pushing."
The Hawks cut a 16-point deficit in the third quarter to 80-79 on a driving layup by Smith with 8:27 remaining. Atlanta didn't make another field goal, going 6-for-6 from the free-throw line.
Philadelphia responded with a 14-2 run, keyed mostly by its bench, to take a 94-81 advantage with 4:04 left. Lou Williams, Theo Ratliff and Speights had four points apiece during the spurt.
"I thought our big guys off the bench really picked it up and did a nice job," DiLeo said. The Sixers led 49-33 late in the first half before cruising to a 51-37 advantage at the break. Johnson and Mike Bibby combined to shoot 0-for-10 in the first half.
Sixers center Samuel Dalembert played in his 263rd consecutive game, despite a right calf strain. Miller played in his NBA-leading 521st straight game. Dalembert is currently third in consecutive games played. ... DiLeo is 29-21 since taking over for Maurice Cheeks. ... Hawks guard Acie Law (lower back pain) was inactive. ... Atlanta was 21-of-21 from the free-throw line.