SAN ANTONIO -- With his team mired in a double-digit losing streak, San Antonio Spurs coach Gregg Popovich has tried shaking things up with his starting lineup.

On Friday, that meant moving rookie sensation Victor Wembanyama to the center spot and surrounding him with four perimeter players in the starting group for the first time this season. But despite the move, the result stayed the same.

The Spurs dropped their franchise-record-tying 16th consecutive game, a 121-112 loss to the Chicago Bulls. San Antonio is 3-18 this season, their worst start in franchise history through 21 games.

They lost despite a huge night from Wembanyama: 21 points, 20 rebounds, 4 assists and 4 blocks. At 19 years and 338 days, he became the youngest player in NBA history with a game of 20 points and 20 rebounds, passing the mark held by Dwight Howard in 2005 by just four days. Wembanyama and Howard are the only teenagers in league history to reach 20-20 in a game.

The Spurs led by as many as 12 but ultimately slowed down in the second half, in what has been a common trend this season. The Spurs are 1-9 in games they've held at least a 10-point lead, with eight straight losses.

Once again, the Spurs couldn't get things going in the third quarter when the Bulls outscored them 35-20 to take the lead. San Antonio briefly led in the fourth quarter, but Chicago was able to pull away late.

"When our opponents are down at half, of course they're going to try and have a reaction, but we got to expect that every time," Wembanyama said. "Because our first half was pretty solid, especially defensively. And yeah, there's ups and downs during the game, but we got to get our downs less and less."

Through 21 games, San Antonio has been outscored by 146 points in the third quarter. The team with the worst point differential in the third quarter last season was the Miami Heat, at 156.

"It's been a combination of things," Spurs guard Tre Jones said of his team's third-quarter struggles. "Turnovers, I think is something that's consistent. Tonight, [offensive] boards throughout the entire game, but obviously in the third quarter as well. We stopped hitting shots as well and they just picked up their physicality and ended up getting to the free throw line as well. It was just a combination of things and that's where it turned again."

Jones finished with 18 points and 9 assists but was not part of the new lineup change Popovich made.

The Spurs started Wembanyama at the center spot along with Devin Vassell, Malaki Branham, Keldon Johnson and Jeremy Sochan, who was reinserted into the starting group after sitting in Wednesday's loss to the Minnesota Timberwolves.

Popovich said pregame that with the new lineup, "there is really no point guard." Sochan, who has been the Spurs' de facto starting point guard this season, shared ballhandling duties throughout the night.

Despite the impressive showing on the glass from Wembanyama, San Antonio allowed 24 offensive rebounds to the Bulls.

"It's a lot of extra possessions that you have to fight through," Popovich said. "So that was the poorest part of the game. Our rebounding. But a lot of guys are doing better things and improving, but we can't forget the basics. Rebounding. That's pretty basic."

Popovich said the offensive rebounding had nothing to do with just playing Wembanyama as the lone big man for long stretches, pointing to several missed box outs on the wings that led to second-chance points for Chicago.

It does appear the Spurs will stick with this starting lineup for the near future. Wembanyama said he's looking forward to being used at the center position.

"Experimenting in different areas of the game. It's always something important and interesting to me," Wembanyama said. "Every game is different, but we're going to see and try until we find a good recipe."