SANTA CLARA, Calif. -- No rookie class took more snaps in 2017 than the San Francisco 49ers' first-year players. Perhaps that was to be expected on a rebuilding team, but with so many of their rookies getting valuable repetitions, the Niners got a lot of production -- finishing second in the NFL in approximate value gained by rookies -- from a group that should contribute in the years to come.

Grade: Above average

Best rookie: LB Reuben Foster -- The dynamic and charismatic Foster was one of the league's most exciting rookie defenders when healthy in 2017. An ankle injury slowed him early but when he returned, he was easily the team's best tackler and proved solid in coverage. The offseason will be important for Foster to refine his tackling technique to help avoid some of the nagging injuries that plagued him throughout the season. Having a full offseason for the first time (shoulder surgery limited him last year), should also allow Foster to make the move to middle linebacker, the spot the Niners hope he'll control for years to come.

Most improved rookie: CB Ahkello Witherspoon -- Witherspoon took some time to get up to speed as he was a healthy scratch early in the season. But Witherspoon got better from week to week and eventually elbowed his way into some playing time before claiming a permanent starting job. There were still some ups and downs that followed, but Witherspoon was the Niners' best cover corner by the end of the season and answered most questions about whether he'd be physical enough to help in run support. He looks to have one starting job at outside corner nailed down for the foreseeable future.

Most disappointing rookie: RB Joe Williams -- After the draft, there were some who believed Williams would immediately challenge Carlos Hyde for the starting job or, at least, begin working in a time share situation before claiming the job permanently. Instead, Williams was underwhelming in the preseason then landed on injured reserve with a foot injury. That ailment didn't seem serious enough to keep him out all year but the Niners clearly didn't want to risk exposing Williams to waivers so he got the season to get back to full strength. Still, it's fair to wonder where he fits moving forward.

Jury is still out on …: DE Pita Taumoepenu -- The 49ers kept Taumoepenu on the active roster out of training camp as much for fear of losing him to another team as for his expected ability to contribute as a rookie. As such, Taumoepenu was only on the active game day roster twice this season and did not play a single defensive snap. Defensive coordinator Robert Saleh said recently he's excited to see Taumoepenu get an offseason to bulk up and hone his technique. He'll need a big offseason in order to have a chance to contribute next year.

Undrafted rookie evaluation: After the draft, general manager John Lynch referred to the Niners as a "land of opportunity" for undrafted free agents and that's exactly what it turned out to be. Running back Matt Breida, receivers Kendrick Bourne and Victor Bolden Jr., offensive linemen Erik Magnuson and Darrell Williams Jr. and tight end Cole Hikutini all spent at least some time on the active roster. Breida emerged as the primary backup to Hyde while Bourne came on near the end of the season.