Then his ACL gave out.
The second-year running back reported to training camp this week healthy and ready to be a full participant after the Vikings brought him along slowly this offseason. Cook even shed the knee brace.
"I really got comfortable [without the brace] over the offseason," Cook said, via the team's official website. "I told myself, 'I know the work I put in, I'm going to test it out before I get back to camp,' so I tested it out and felt comfortable with it. I just went forward and let [Vikings director of sports medicine Eric Sugarman] and the training staff know that I wasn't going to be wearing it. They are comfortable with it as long as I was comfortable with it."
In just three and a half games as a rookie, Cook showed the ability to be a workhorse runner with pass-catching ability.
New offensive coordinator John DeFilippo likes what he's seen in limited time with Cook.
"He looks really good," said DeFilippo, who was hired this offseason. "Looking forward to him getting the pads on and seeing where Dalvin is at. We expect him to be full-go."
While Latavius Murray might spell Cook on some early downs, expect the second-year back to become a three-down workhorse. One of the key aspects for young backs in earning that every-down role is pass protection, where most first- and second-year players struggle. DeFilippo gave Cook a glowing review in that area.
"He got in to the blitz period yesterday, and he was assignment perfect," DeFilippo said of Cook. "I think that when you see a young player that understands protections the way he does at an early age, I think that's really unique. Obviously he has the pass-catching ability that we've all seen, but a lot of times when you play that running back position, I think pass protection sometimes gets overlooked."
If Cook starts the season healthy, the Vikings will own difference-making weapons at every level of the offense.
After years of working without a running game in Washington, Kirk Cousins will finally have a franchise back lining up behind him.