For the fourth time in six games this season, Brock Purdy won’t play quarterback for the San Francisco 49ers. Purdy has a toe injury and did not practice for Sunday’s game against the Tampa Bay Buccaneers.

That would put Mac Jones back up for the 49ers. But the former Alabama All-American never got past limited participation in practice over the past week, still hadn’t thrown the football as late as Thursday and received a questionable designation for his game status because of knee and oblique injuries.

At his Friday press conference, San Francisco coach Kyle Shanahan was asked when he would determine if Jones would play against Tampa Bay.

“Pretty much already have,” Shanahan said. “But you got to put it that way if there’s any doubt at all. So pretty much already have.”

Shanahan wouldn’t explain what was keeping Jones from throwing.

“I do know, but I don’t have to tell,” Shanahan said, “so has to do with his knee-slash-oblique.”

Jones said he was saving it for Sunday, with 49ers quarterbacks coach Mick Lombardi handling some of the practice load at QB.

“Just trying to save some throws,” Jones said on Thursday. “And, you know, there’s a lot of volume out there and, at the end of the day, got to be ready for Sunday.”

Asked to assess his health, Jones said: “Working through it. I think, like I said, got a plan with the training staff and been getting treatment every day and trying to do everything I can — sleep, eat, do the little things — and everyone else is doing the same thing. So that’s NFL football. …

“Definitely feel like I have a good plan in place, and the game’s on Sunday and we’ll see how I feel when we get there.”

In an interview with NBC Sports Bay Area, Shanahan made it sound as though Jones would play through anything.

“No matter what happens,” Shanahan said, “no matter how many bananas he needs or pickle juice, whether he’s dry-heaving or his pants are falling off, he just keeps going. He’s a tough quarterback.

“Mac was a really good coming out of college, and he’s shown in this league he can play at a high level, and he’s doing it again.”

All those things were part of the story of the 49ers’ 26-23 overtime victory against the Los Angeles Rams on Oct. 2, with Jones throwing for 342 yards and two touchdowns.

“That’s part of football is playing tough,” Jones said, “and the tough part is getting back and having to do it the next week.”

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The 49ers have won all three of Jones’ starts this season, and he’s averaged 301.7 passing yards per game, the top mark in the NFL.

“Every game, you have a plan for what you need to fix and what you need to get better at not only on the field but off the field with your body and how you feel,” Jones said. “So for me, just getting treatment every day and working and we have a good plan in place and I feel confident and just working through it day-by-day. And that’s all you can do.”

Jones’ backup is Adrian Martinez, the former Birmingham Stallions quarterback who won the United Football League Most Valuable Player Award and helped the team win its third consecutive league championship in 2024.

“This week’s been nice for him because he’s got a lot more reps with the ones just filling in for Mac and stuff,” Shanahan said. “So we’ve been able to see him on tape more instead of just running cards and things like that. So got a better feeling this week than I have in the past few weeks.

“You always try to keep it as simple as you can for guys in that situation. Give him certain things, tell him things, he tells you things he’s the most comfortable with and then you try to isolate on that stuff. But when you get into a game, it’s about the situations.”

The 49ers and Buccaneers square off at 3:25 p.m. CDT Sunday at Raymond James Stadium in Tampa, Florida. Alabama’s CBS affiliates are scheduled to televise the game.