For just the second time on Wednesday, NFL rules allowed second-year cornerback Mackensie Alexander to line up across from receiver Stefon Diggs during Vikings practice.

Football is just getting started at Winter Park.

As are the many competitions we'll continuing updating throughout the summer. One of the more intriguing and important roles left open by free agency falls in the middle of the defense. Captain Munnerlyn provided an underrated service for three seasons in Minnesota as the nickel cornerback, tasked with defending smaller, quicker receivers with no help from a sideline to dictate direction.

It's perhaps the biggest hole left in the defense from departures this offseason as Munnerlyn played about 60 percent to retired linebacker Chad Greenway's 40 percent of snaps. Anticipating Munnerlyn's exit, the Vikings drafted Alexander in the second round in 2016 and are now evaluating him, among others, to take over in the slot.

"Right now we have a number of guys working in there," defensive coordinator George Edwards said. "As we progress through this offseason, competition at the position will come to the top and we will look forward to going through that process."

The 23-year-old Alexander started the Vikings offseason program last month without a hitch after last season ended on injured reserve and surgery to repair a lingering groin issue he'd dealt with since Clemson. While he should be considered the front-runner, Alexander won't be handed the job.

Head coach Mike Zimmer has another talented pupil in Alexander, who took some rookie lumps in only 68 defensive snaps last season. After showing promise in the preseason, he didn't play more than 18 defensive snaps in a game. He was penalized twice on defense and, after not allowing a touchdown in his final 23 college games, Alexander surrendered one in fewer than 40 snaps in the NFL.

The Vikings turned to 38-year-old veteran Terence Newman to fill the slot role when Munnerlyn needed to sit out Week 10 at Washington. They could do so again this season as Newman rotated into the slot with Alexander during Wednesday's OTA practice. Cornerback Jabari Price is also in the mix.

The ageless Newman, who held a starting job for two years from fellow first-round pick Trae Waynes, could once again help the Vikings as they bring along another young cornerback at his own pace.