CHARLOTTE, N.C. (AP)Baker Mayfield limped to the podium following the Carolina Panthers’ 37-15 loss to the San Francisco 49ers, his left foot in a walking boot. The quarterback said he plans to have an MRI on Monday to determine the extent of the injury.

The former No. 1 overall pick struggled again Sunday, completing 20 of 36 passes for 215 yards with an interception that was returned 41 yards for a touchdown by 49ers cornerback Emmanuel Moseley. Mayfield has four touchdown passes and four picks in five games for the Panthers (1-4), who have lost 11 of their last 12 games under coach Matt Rhule.

And now he’s injured.

Mayfield’s ankle got rolled up on late in the first half, but he returned to play in the second half, leading the Panthers to a touchdown on the opening drive of the third quarter. He remained in the game until the final few minutes when he was replaced by P.J. Walker with the game out of hand.

”Somebody landed on the ankle,” Mayfield said. ”It didn’t feel too good.”

With Sam Darnold still on injured reserve and at least a couple of weeks away from returning from his own ankle injury, Walker would be in line to start if Mayfield can’t play next Sunday against the defending Super Bowl champion Los Angeles Rams.

Walker is 2-0 as the Panthers’ fill-in starter the last two seasons.

”I have a walking boot on, my leg is not cut off so I will be all right,” Mayfield said. ”I would love to be in a better position record-wise but you keep pushing forward. It’s not time to put your head down and give up.”

Carolina’s passing game has been a wreck all season.

The Panthers came into the game ranked last in the league in offense and 31st in passing. Mayfield’s total quarterback rating was last in the league and he didn’t do much to help those numbers on Sunday as Carolina averaged 5.1 yards per pass play.

”It’s a lot of frustration,” Mayfield said. ”And the more you think about it, angry because we haven’t played to our capability. That’s the frustrating part – we have to translate it to Sundays. You work all week and you come out on Sundays and you have to make plays.”

Rhule didn’t elaborate on Mayfield’s injury.

Mayfield’s biggest mistake came late in the first half when he overthrew Christian McCaffrey and was intercepted by Moseley, who returned it for a score and a 17-3 49ers lead.

Rhule called it a ”gut punch” and Mayfield agreed, saying the pass was just a little high.

Mayfield hurt his ankle a few plays later. He said he didn’t get a painkiller shot in the locker room at halftime, but was able to fight off the pain. He led Carolina to its only touchdown on the opening drive of the third quarter.

”I’m confident in where I’m at, but I haven’t played well enough obviously,” Mayfield said. ”There is a lot of ball left and we just have to get it fixed. That is how I’m wired. I don’t live in the past, I live in the moment.”

The question may be how many moments Rhule has left. He is 11-27 in his three seasons with the Panthers.

”We’re fine in the locker room when it comes to that,” Mayfield said. ”There are a lot of plays that we just have to flat-out make – and he can’t do that. He can’t go make plays for us. He can’t do the execution for us.”

More AP NFL: https://apnews.com/hub/nfl and https://twitter.com/AP-NFL