FOXBOROUGH, Mass. — Tom Brady watched his backups get plenty of playing time in the New England Patriots’ exhibition opener Thursday night.

The conclusion was clear: Brady better stay healthy.

Ryan Mallett struggled in a 23-6 loss to Washington in his fourth straight year as Brady’s understudy.

Jimmy Garoppolo had some impressive throws but is a rookie second-round draft choice and has a lot to learn.

“Particularly with young players, just because they make a mistake doesn’t necessarily mean that those mistakes will continue and are always going to be there,” Coach Bill Belichick said Friday. “I think we’ve seen that with pretty much every young player, including him.

“I think there were some things he did well last night. I think there were some other things that he learned from.”

Garoppolo played the entire second half, completing 9 of 13 passes for 157 yards and one touchdown. Mallett played the first half and was 5 of 12 for 55 yards. Brady watched it all.

“I feel good,” Mallett said. “I feel comfortable. Everything slowed down. (I) went through my reads. There were throws I could have made better but I felt all right.”

When the Patriots drafted Garoppolo from Eastern Illinois, speculation grew that Mallett might be trade bait. But he said he wasn’t auditioning for another team.

“I’m playing for the Patriots,” he said. “I’m playing for my team.”

Brady’s previous backup, Brian Hoyer, threw just 43 passes from 2009-11 and is competing with Johnny Manziel for the starting spot with Cleveland.

Before that, Matt Cassel threw 39 passes for the Patriots from 2005-07, then nearly took them to the playoffs the following season after Brady suffered a season-ending knee injury in the opener.

Garoppolo, the latest contender for the No. 2 job, must adjust to a new game speed.

“It was definitely fast, faster than college, that’s for sure,” he said. “It’s something that you just have to adapt to, though. You have to adapt quickly in this environment and we’re doing a good job of that, I think.”

Mallett has been better than Garoppolo throughout training camp and both have three more preseason games.

“I did all right,” Garoppolo said. “There’s a lot of stuff to improve on. It’s a process for any quarterback. There’s lots to learn from.”

A less-heralded youngster had a solid performance.

Receiver Brian Tyms signed July 27 with the Patriots after being released by the Browns. He caught two passes for them in seven games last season. He had already been cut by San Francisco and Miami after signing as an undrafted free agent in 2012.

On Thursday night he led the Patriots with five catches for 119 yards, including a 26-yarder for a touchdown.

“Brian ran a great route,” Garoppolo said. “The line gave me plenty of time. I don’t think anyone was even near me.”

Barring injury, the Patriots probably have one vacancy at wide receiver. At 6-feet-3, 204 pounds, Tyms has the size the Patriots lack at that position.

“I feel like I’ve got a good connection with everybody. That’s really all I came here to do was earn respect from my teammates and my coaches,” Tyms said. “If I sit out there and drop every one, everybody (is) going to look at me like I just came here for nothing. So I’ve got a lot to prove.”

The game followed three days of joint practices at Washington’s training-camp facility in Richmond, Virginia.