Jerick McKinnon is the 49ers' ultimate wild card. He can take Kyle Shanahan's offense to new heights, but whether he can stay on the field is the real question. 

General manager John Lynch remains cautiously optimistic. Since McKinnon signed a four-year, $30 million contract on the first day of free agency in 2018, he hasn't played a single game after dealing with a torn ACL before two straight seasons. 

“I think there’s always that critical last juncture of a rehab where you go from running straight ahead and even trying to simulate some of the cutting that goes on at that position, specifically,” Lynch said on The 49ers Insider Podcast. 

“Then, you go play football and it becomes much more reactive. And that’s where he struggled. He’s continued to put in work. There are some positive signs that we’re on a better track.”

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Last year, McKinnon never became comfortable with side-to-side movements and quick-twitch bursts. A workout video posted Saturday shows the 49ers running back appears a lot more comfortable with movements that require more than just straight-line speed. 

McKinnon is seen shuffling, accelerating out of his stops and making quick juke moves. This has to be a positive sign for the 49ers' front office.

To prove he still can play and be a solid part of San Francisco's offense, McKinnon, who was scheduled to make $6.8 million in salary and bonuses in 2020, agreed to a $910,000 base salary this offseason. The next stop on his comeback trail is working out with Washington running back and former NFL MVP, Adrian Peterson. 

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McKinnon caught 51 passes for 421 yards the last time he played a full regular season in 2017. He also rushed for 570 yards that season. His dual-threat ability is exactly what Shanahan wants in his offense. 

And recent videos show "Jet" very well could make a strong impact on the 49ers' deep backfield this season.