San Francisco 49ers running back Joe Williams spent his rookie NFL season on injured reserve. It was an opportunity to ready himself to compete for a roster spot in 2018.

While an ankle injury landed Williams on injured reserve, he recovered fairly quickly but was kept off the active roster so he could work on becoming a better NFL running back. Despite Kyle Shanahan previously saying that Williams has always been in good shape, the 49ers head coach was impressed with how much better he looks this offseason.

"Joe has come a long way," Shanahan said on Tuesday. "I think his body looks a lot better than it did last year. He's put on a lot of muscle mass just with how he's worked and has taken advantage of the year of not playing. I think he has just a different mindset, understands a little bit more of the standard of the NFL, and the difference.

"Sometimes it takes guys time. It's not always malicious. It just takes time to understand it and what you have to do day in and day out. I think Joe has made some huge strides between now and last year. I think that's why he'll have a chance."

Shanahan and running backs coach Bobby Turner were excited to draft Williams last year. Despite an initial reluctance on the part of general manager John Lynch, Shanahan pushed for the selection of Williams. The 49ers head coach still sees the traits in his young running back that made him such an attractive draft pick.

"Joe's an extremely explosive back," Shanahan said. "Look at his yards per carry in the preseason last year. I don't think it was a surprise that he was close to seven (it was actually 5.2, but he did average 8.6 on seven carries during the first week of preseason) and had more than most of the guys. Because when [the play] is blocked right, he's got the burst to get through there as fast as anyone.

"But it's just about doing it day in and day out and protecting the football. What do you do when the run doesn't look good? What do you do without the ball in your hands? And just everything. Just being the same guy every day and Joe's come a long way in this year, and I'm excited about him coming back to training camp."

As for the 49ers' big offseason acquisition, running back Jerick McKinnon, Shanahan has loved what he has seen so far this offseason.

"Jerick's been great," Shanahan said. "He missed some time. We were pretty cautious with him with some ankle stuff in the middle of OTAs, but he's got enough reps, and he's been what we hoped."