Just imagine where he'll be once he's comfortable.
"No matter what system he's in, there's going to be a learning curve," Popovich said. "It's the third game of the season."
Guard Danny Green knows it'll take time.
"We're all still trying to figure it out," he said. "It's still going to take some time. We're still trying to figure it out. Even the old guys that have been here are trying to figure it out."
Aldridge was signed by the Spurs to a four-year deal after he spent nine years in Portland. Boston coach Brad Stevens thinks the Spurs will be even tougher once Aldridge gets used to his new teammates.
"He disrupts it because he's an all-league player," Stevens said. "I think the biggest thing is that, as they're figuring each other out, they're not as crisp as they will be in three months, four months, but they're still awfully good."
Aldridge had eight points in the final period as the Spurs held off the charging Celtics.
San Antonio opened a double-digit lead early in the game, but the Celtics closed a 14-point, fourth-quarter deficit to four points three times in the final 4 minutes, the last on Smart's 3-pointer from the right corner that made it 86-82 with 2:45 to play. But then Leonard nailed a jumper and Tony Parker had a fast-break layup with 2:02 to go.
The Celtics shot 35.7 percent in the game and missed 23 of 29 3-point attempts.
"As a group, we couldn't hit shots," Thomas said. "Then, when we did get back into it, you've got the Spurs making shots."
The Spurs had a 13-point halftime lead sliced to seven by Boston's 8-0 run early in the third, but San Antonio pushed it back to double digits 2 1/2 minutes later.
The Spurs led 64-54 after three quarters.
Spurs: It was their first of three road games in four days. They are opening the season with six of their initial eight away from home.
Celtics: F Kelly Olynyk was the 11th player to see action for Boston. On Friday, he was one of the first two subs. ... Thomas, who averaged 26 points in Boston's first two games, was just 1 for 9 from the floor in the first half.
Boston missed 17 of 23 shots in a slow first quarter. The Spurs held a 3-2 lead over 5 minutes into the game before pushing it to 23-13 at the break.
In the first half, San Antonio shot 37 percent, but held a 44-31 edge at intermission because the Celtics hit only 29 percent (14 of 48), missing 11 of 12 on 3-point attempts.
THE BEST TRIO
Before the game, Popovich talked about a photo of former Celtic and Hall of Famer John Havlicek that he has hanging in his office in San Antonio.
"I brought it with me from Pomona-Pitzer when I came to San Antonio and I put it up again," he said. "In that room, there's a chair and a table and a lamp -- and there's a picture, and it's been there for the last 18, 20 years. It's John Havlicek, so I do think about the legacy here."
Spurs: At the New York Knicks on Monday.
Celtics: At Indiana on Wednesday.