Young, a second-year swingman from USC, made his first five shots and finished 7-of-8 from the floor. Young had missed the first five preseason games with a sore left knee. Arenas is out with a knee injury.
"I felt good out there," Young said. "I got it going a little bit. I was kind of nervous going out there in the beginning. I haven't played in a while. It felt good. It felt right."
Roger Mason, a free-agent acquisition who's expected to find a regular spot in the Spurs' rotation after two seasons in Washington, knew Young had plenty of talent.
"You would see that every day in practice," Mason said. "With him it's not a matter of his talent. It's a matter of him applying it everyday. I think he's going to be fine."
Washington also got 15 points in 23 minutes from Caron Butler, who has scored in double figures the past two games.
The Spurs were led by Tim Duncan's 20 points in 22 minutes. Duncan, who made 8-of-9 free throws, also grabbed eight rebounds.
The Wizards made 4-of-5 3-pointers to start the game and finished 10-of-19 from beyond the arc. Washington (2-4) is trying to avoid its worst preseason since a 2-6 record in 2003-04.
Each team finishes the preseason on Friday.
The Spurs (3-3) are trying to avoid their first losing preseason since 2005-06 when they were 2-7.
Washington led by as many as 18 points in the fourth quarter. The Spurs cut it to 94-90 on Desmon Farmer's 3-pointer with 2:16 to play.
The Spurs trailed by six with 2:34 left in the third quarter. But the Wizards expanded the lead back to double digits when Darius Songalia and Juan Dixon made jumpers on consecutive trips down the floor.
Young proved tough to guard after that. He made a 19-foot jumper and followed with a drive and dunk to make it 79-65 with a minute left in the third quarter.
"He has fresh legs," Wizards coach Eddie Jordan said. "He's a lot more familiar, obviously from last year, in what we're doing. He has more of a professional approach than last year. He's serious in his approach and preparation and it shows."
Young appeared in 75 games last season, starting two.
"I had to dunk (tonight)," Young said, "to let the coaches know I'm back, get the confidence in my knee, let them know I'm 100 percent. Show them I'm good."
He wasn't the only young player to make an impression for Washington. JaVale McGee finished off a 3-point play with 6:24 to go before halftime to increase the Wizards lead to 12.
McGee, a 7-foot rookie out of Nevada taken with the 18th pick, finished 4-for-6 and hit his three free-throw tries to finish with 11 points.
"We've got a lot of the young guys," Butler said. "Nick Young went out and played exceptional. JaVale McGee is doing a lot of positive things. Our energy level defensively and collectively -- we looked great."
The Spurs cut it back to 47-43 when rookie Malik Hairston made a 16-footer with 2:31 left.
But Young scored the final five points of the half on a 3-pointer and a short jumper on the fast break to give the Wizards a 52-43 lead at halftime.