Pro Football Focus currently ranks San Francisco 49ers center Weston Richburg as the No. 30 center in the NFL. Head coach Kyle Shanahan knows only so much stock can be put into analytics sites which grade players without knowing their assignments on any given play. That makes it particularly difficult to evaluate offensive linemen.

Shanahan believes the 49ers have a good center in Richburg, who signed a five-year deal with San Francisco in March after spending his first four seasons with the New York Giants.

Shanahan was asked on Wednesday about the perception of Richburg because of his low analytics grade.

"I'm not sure because I don't really know how they grade it," he responded. "So, I couldn't tell you that. But, I know that I'm happy with him. Doesn't mean that there's not room to grow. I think he could play better, too, especially the way he started out the year. We've got to find out a way to make that last throughout the whole year. But no, I think we've got a very good center who is only going to get better."

Richburg, like much of the 49ers roster, has been plagued by injury this season. His name has frequently appeared on practice participation and injury reports this year due to an ongoing knee injury. Richburg, however, has only missed one game this season — a Week 8 matchup against the Arizona Cardinals.

"I know he started off this year at an extremely high level," Shanahan said. "I thought he was doing as well in the run game and stuff at the beginning of the year as anyone I've had. Had a number of setbacks with his knee injury that he's battled through. I think he only missed one game because of it, which is a credit to him because it's been tough for him to practice for a lot of this time.

"I think he's starting to get healthier, which he's finishing stronger than the little stretch he had to the beginning. I think it'll help him a lot more being a year in our offense, too, just coming back next year."

Shanahan isn't sure whether or not Richburg will require offseason surgery.

The Giants made Richburg a second-round pick out of Colorado State in 2014. This year's grade is the lowest of his career, according to Pro Football Focus. Richburg's grade against the Bears this past weekend, however, was his third-highest during the 2018 season.