Jamal Murray led the Nuggets with 31 points, Nikola Jokic had 19 points, 13 rebounds and six assists and Gary Harris added 17 points for Denver (19-17).
Trey Lyles added 16 points and eight rebounds for the Nuggets.
The Sixers improved to 2-7 without center Joel Embiid. Embiid flew straight from Portland to Phoenix, where Philadelphia plays on Sunday night. Coach Brett Brown said Embiid went through a workout Saturday and will be ready to go against the Suns.
Philadelphia (16-19) missed its first nine shots of the third quarter -- and 10 in a row overall -- when the Nuggets went on an 11-0 run to take a 14-point lead. The Sixers didn't get their first points of the second half until nearly five minutes in, and those came on free throws by Saric.
Saric broke the field goal drought with a 3-pointer as Philadelphia responded with 11 straight points and a 25-4 run to make it take a seven-point lead late in the third quarter.
The run was aided by poor foul shooting by Mason Plumlee, who was shooting 40.2 percent from the line and was 1 of 7 against the Sixers.
The run extended to 33-7 into the fourth thanks to Bayless, who hit a 3-pointer and two field goals to turn a three-point lead into a 91-80 advantage.
Jokic made two free throws with 1:01 left to get Denver within 103-100 but Will Barton missed a tying 3-pointer with 25 seconds left.
Covington, who finished with 15 points and 10 rebounds, hit two free throws with 19.5 seconds left.
NOTES: Philadelphia coach Brett Brown said the decision to sit C Joel Embiid on one end of back-to-back games is medical. "It's all pointed towards health," Brown said. "When you play a game and you have a chance to have a day or multiple days in between that can better allow him to play whatever game it'll play out to be, then that's the answer. It's really as simple as that." ... Denver G Malik Beasley (right elbow sprain) was dressed and available. F Juancho Hernangomez (illness) was inactive.