Jayson Tatum scored 34 points, including a go-ahead basket with 33.7 seconds remaining on Saturday as the Boston Celtics escaped San Antonio with a 121-116 NBA victory over the tenacious Spurs.

While the Celtics followed up a dominant victory over the Dallas Mavericks on Thursday, the Mavs bounced back with a 127-117 victory over the New Orleans Pelicans with the help of a triple-double from Luka Doncic.

The Celtics improved their league-best record to 28-12 as they finished up a 2-2 road trip — but it looked harder than it needed to be against a rebuilding San Antonio squad.

Jaylen Brown added 29 points, and Malcom Brogdon scored 23 off the bench, his contribution gaining importance after Marcus Smart exited early with an injury.

Robert Williams scored 10 points, pulled down 11 rebounds and blocked four shots for the Celtics, who led by 11 midway through the fourth quarter.

The scrappy Spurs — who had 18 points apiece from Zach Collins, Tre Jones and Josh Richardson – tied it up at 116-116 on Richardson's three-pointer with 37.4 seconds remaining.

Tatum's step-back basket — off a pass from former Spur Derrick White — restored Boston's lead, and three Celtics free throws sealed it.

"There's obviously a lot of stuff tactically we can work on," said Celtics coach Joe Mazzulla, who nevertheless insisted he was happy to see his team work through adversity to get the win.

"We needed a game like this, to where it's back and forth, things aren't going our way, they are going our way — you don't get a lot of those."

"It's easier to say that because we won," he acknowledged. "But I'm happy the game went the way it did because we got to execute some stuff."