Center Weston Richburg had a long road back after undergoing knee surgery in January. San Francisco 49ers head coach Kyle Shanahan explained on KNBR on Tuesday that surgeons had to repair Richburg's knee and reattach his quadricep. It was far from a minor procedure, and the center's injury was perhaps far worse than most realized at the time.

San Francisco activated Richburg off the Active/Physically Unable to Perform (PUP) list on Monday, and he has taken part in two practices this week. Shanahan feels the practices have gone well but that Richburg is not all the way back just yet.

The 49ers will hold a walkthrough on Wednesday. They will also have players who will not play in Thursday night's preseason finale go through a light practice. Richburg will be part of that group.

"We were very patient with [the recovery], and he came out yesterday (Monday) and got about 15 reps, just going one-on-one versus a couple of our players," Shanahan said. "Then today (Tuesday), he came out and got about 20 more reps, and it's been great. I feel very good about him coming back.

"The main thing with him is, does he have enough time to get in football shape? He's passed the test here two days in a row. We'll continue to do that.

"Guys who aren't dressing in the game (on Thursday), we'll practice them a little bit tomorrow. We'll have another one on Saturday. Then we come back on Monday with our final 53 and everyone. Then it will be all Tampa going forward with that."

The 49ers signed Richburg to a five-year deal on March 13, 2018, worth up to $47.5 million. He started 15 games last year despite dealing with his injury throughout most of the season. Shanahan and the 49ers hope to have Richburg available for their Week 1 contest against the Tampa Bay Buccaneers on September 8 but will do what is best for the team long-term.

"We'd love to have Richburg there, available, if it's close," Shanahan continued. "If we don't feel good about it, then we feel very good about Ben Garland. That's why we were fortunate enough to get him this offseason. He's done a good job at center while Richburg has been away. We can't wait to get Richburg back, but we're going to be smart with that, and made sure we don't rush him back if we don't feel it's in his total best interests."

You can listen to the entire conversation with Shanahan below.