Mac Jones, who is in line to start a fourth game for the Niners should Purdy be unavailable, was limited in practice Thursday for a second straight day as he deals with left knee and oblique ailments.

Although Jones expressed optimism Thursday that he'll be available to start against the Buccaneers, he also made it clear that he's still in the midst of recovering.

"(I'm) just getting treatment every day and working," Jones said. "I feel confident and just working through it day by day. That's all you can do."

Jones played through the knee issue in last week's win against the Los Angeles Rams but indicated Thursday that the oblique injury happened at the end of the game, which left it unclear whether he'd have returned had the offense gained another possession.

Given a couple of extra days of rest coming off that Thursday night game, Jones said he has been focused on getting treatment every day and doing all the little things he can to help his recovery such as monitoring his sleep and what he eats in an effort to help the cause.

On Thursday, that included doing little throwing during the individual drills open to media. While Jones did some soft tossing during the first period when light warm ups are going on, he did not do any throwing during the third period of practice when the quarterbacks are throwing to receivers running routes.

"I was just trying to save some throws and there's a lot of volume out there," Jones said. "At the end of the day, (I've) got to be ready for Sunday."

With Jones taking a reduced practice work load and Purdy not participating again (though he was seen doing some conditioning on a side field), Adrian Martinez got snaps with the first-team offense. Martinez has served as Jones' backup in his three starts this season and was promoted to the active roster from the practice squad on Oct. 2.

Martinez has not played in a regular season game and has only been with the Niners since signing to the practice squad on Aug. 28. Offensive coordinator Klay Kubiak said if Martinez has to play against the Bucs, he is far enough along where he wouldn't be overly limited by his relatively recent arrival.

"I think he's right where he needs to be," Kubiak said. "Super impressed with Adrian since he's been here. Really smart guy. He's gotten a little more reps just because of Mac kind of progressing a little bit through the week and Adrian hasn't missed a beat. He's been on it. I feel like he can go out there and run our offense."

In last week's game, there were multiple moments when it appeared Martinez would have to replace Jones. Considering what he's dealing with again this week, it's reasonable to think that Martinez will again have to stay at the ready even if Jones starts as expected.

Jones, meanwhile, remains hopeful that another couple of days will have him feeling better.

"The game is not today, right?" Jones said. "I don't really do the theoretical questions but definitely feel like I have a good plan in place. The game is on Sunday and see how I feel when we get there."

Elsewhere on the injury report, 49ers receiver Jauan Jennings (ribs, ankle) and defensive tackle Alfred Collins (knee) returned to limited practice after not participating on Wednesday.