The San Francisco 49ers had an extra coach on the field during Tuesday's practice. Richard Sherman, the former Seattle Seahawks cornerback who signed with the 49ers in March, is still recovering from a ruptured Achilles suffered in November. He has not been medically cleared to practice with his new teammates.

Instead of practicing or merely being an observer, Sherman was seen working extensively with the defensive backs on the team while offering advice to the younger players.

"It's always nice when you have someone who has a lot of experience in a very similar system," head coach Kyle Shanahan said on Tuesday. "The foundation of it all came from the same spot, and when you've got a guy who's played in it that long, and really started in that system, and has kind of excelled in it as good as anyone, it's nice to have."

One of those young defensive backs, Ahkello Witherspoon, is excited to have the opportunity to play across from Sherman. Witherspoon ended his 2017 rookie season as one of the 49ers' starting outside cornerbacks.

"It's incredible the way it worked," Witherspoon told reporters following Tuesday's practice. "All I wanted throughout college was to play across from Sherman. He was an idol of mine, and now seeing him every day; he's just a regular dude. Still great, don't get me wrong. Just to have that opportunity to learn from him, to pick his brain, that's all I craved.

"In terms of playing across from him? I just wanted it so I could understand what he knows and learn the game from how he sees it, to build on the athleticism and what I already bring to the game."

It's not just the defensive backs who think highly of Sherman. Defensive lineman DeForest Buckner also respects the All-Pro cornerback and cannot wait to see him get back on the football field.

"Sherman's a great guy," Buckner said. "He gets along with everybody. He's very approachable and when he talks, everybody listens. That's the kind of respect everybody has for him in the locker room. His presence alone is real strong. We can't wait for him to get back out there. We're going to feed off of his energy."

Eric Branch of the San Francisco Chronicle posted the following video of Sherman working with Witherspoon and the other defensive backs during Tuesday's practice.