The Vikings traded the Nos. 48 and 128 picks to the Cincinnati Bengals in order to move up, completing a move they had discussed on Friday morning after Cook slipped out of the first round the night before.
"I had a pretty good feeling he wasn't going to last until our pick at 48," general manager Rick Spielman said. "When I went in and talked to [offensive coordinator] Pat [Shurmur] about this being a possibility, his mouth kind of dropped, and so did [running back coach] Kennedy [Polamalu]'s, as well. With the three backs we currently have right now, I think we're going to have some playmakers coming out of our backfield this year."
Peterson signed with the New Orleans Saints early this week after spending the first 10 years of his career with the Vikings.
A 5-foot-10, 210-pounder, Cook ran for 1,000 yards in all three of his seasons at Florida State, including a career-best 1,765 yards and 19 touchdowns as a junior last season.
His slide to Day 2, Spielman said, was prompted by concerns about his injury history and a handful of off-the-field issues at Florida State. He was charged with criminal mischief in 2014 and given pretrial intervention, which he completed. He also was suspended indefinitely after an alleged incident outside a Tallahassee bar in 2015; he ultimately was acquitted of misdemeanor battery.
"I know the incidents that have been reported out there," Spielman said. "He was never charged with the incident, I believe, in the bar. I think that was thrown out within a half-hour. I asked him very pointed questions, and I knew he was sincere and honest with how he answered everything."
Cook dealt with hamstring issues throughout the 2015 season and has had three shoulder surgeries since high school. However, Spielman said the Vikings' doctors had "no concerns" with Cook's medical status after examining him.