Lions running backs coach David Walker this week described second-round pick RB Kerryon Johnson as a "three-down player.”

However, the Lions would like to believe they’re in a spot where they don’t have to use Johnson as an every-down workhorse this early in his career.

NFL teams have traded up for just five running backs in the first three rounds of the last four drafts: Melvin Gordon, Kareem Hunt, Alvin Kamara, Dalvin Cook, and Johnson.

It should be noted it was easier to forecast early volume as rookies for Gordon and Hunt, due to a lack of competition in the backfield at the time. However, at this point last offseason, there was certainly ambiguity in the backfields of Kamara on the Saints and Cook on the Vikings, for Cook at least until mid-to-late August. That type of ambiguity in the backfield can lead to discounts in fantasy drafts, where Johnson is currently being drafted in the eighth round or later. Detroit aggressively traded up for him, using premium draft capital in an offseason where they are looking to overhaul their running game.

Minnesota Vikings running back Dalvin Cook gave an update Tuesday on his surgery to repair a torn ACL. Cook tweeted that his surgery “went great” and thanked fans for their support.

Cook should be able to make a full recovery, and as long as there are no setbacks, should be ready in time for next season.

With Dalvin Cook shelved for the season because of a torn ACL injury, the Minnesota Vikings plan to sign one-time Patriots relevant running back Stevan Ridley.

Ridley's fantasy impact should be zilch, as he'll be nothing more than a depth chart signing and will likely see very minimal playing time behind Latavius Murray and Jerick McKinnon.

Coach Zimmer confirms that Dalvin Cook has a torn ACL.

Related players: Latavius Murray, Jerick McKinnon

Zimmer added he expects Cook to come back and be the same back he was to start his rookie season. He should be ready to go for the 2018 season.

Latavius Murray said his ankle is still not 100 percent and he still has some soreness.

Related players: Dalvin Cook, Jerick McKinnon

Murray stands to have a big increase in workload with the loss of Cook, but the repaired ankle not being fully healed may certainly affect that. It could mean more work for McKinnon who is typically a change of pace and third down back.

The news couldn't be worse for the Minnesota Vikings.

NFL Network Insider Ian Rapoport and NFL Network's Tom Pelissero reported that Dalvin Cook's knee injury is believed to be a nearly complete tear of his ACL based on an initial diagnosis for the rookie running back, per sources informed of the situation.

Cook is "hopeful" a subsequent MRI will reveal otherwise, but chalk Sunday up as a devastating setback for the rookie and his team.

Related players: Jerick McKinnon, Latavius Murray

Murray and McKinnon will likely be hot pickups this week on the waiver wire. Murray finished with seven rushes for 21 yards and did have two catches while McKinnon wasn't much of a factor running twice for no yards and he didn't catch a ball. McKinnon probably makes the most sense for PPR leagues while Murray may be a better standard league fit.

Things quickly went from good to bad to worse for the Vikings in the third quarter today against the Lions.

After Minnesota had jumped out to a 7-3 lead in the third quarter, Detroit cut it to 7-6 with a field goal. On the Vikings’ ensuing possession, it went bad.

Vikings running back Dalvin Cook took a handoff, appeared headed toward a big gain, but then got hit just as he was cutting. Cook’s knee buckled and he fumbled, and the Lions recovered.

Related players: Latavius Murray, Jerick McKinnon

It didn't look good for Cook who went down without contact, fumbled the ball and immediately grabbed the knee area. We'll continue to update but if Cook were to miss time, Murray and McKinnon would see larger roles in the running game.