EAGAN, Minn. — The Vikings defense was on the field for 78 snaps in Sunday's season-opening win against Atlanta, with safeties Harrison Smith and Anthony Harris playing every one of them.

Jayron Kearse played 45 snaps, the majority of which came after slot cornerback Mackensie Alexander left late in the second quarter with an elbow injury and did not return.

Not that Kearse wasn't involved before Alexander's injury.

"Actually I stuck him in there earlier in the game before Mackensie got hurt just because I wanted to get a bigger guy in there," said Vikings Head Coach Mike Zimmer. "It happened to be a run, and he (Kearse) did a really good job on the play and out-physical-ed their slot receiver."

Zimmer said Alexander was getting an MRI on Monday and didn't elaborate. Second-year cornerback Mike Hughes, who played outside and inside as a rookie, was ruled out of Minnesota's Week 1 game.

Kearse offers the Vikings a big option as a fifth defensive back. Although he is still listed as a safety on Minnesota's roster (Kearse showed he could play that position by filling in for Smith in the third preseason game), the former Clemson standout has essentially switched positions in recent years.

"I'm very confident, the same way I was last year. I feel like I can get out there and make plays and cover anybody," Kearse said Monday. "It's really just about getting opportunities. I'm going to have a bit more on my plate now that Mackensie is down right now. I just have to be ready for it.

"Honestly, I've played more nickel than I've played safety," Kearse later added. "For me, if anything, it would be an adjustment the other way around. I've been on the field in actual game action at the nickel position, rather than back deep at safety."

Kearse didn't make any starts in 2018, but he did play 202 snaps on defense, the majority of which came in the slot as part of Minnesota's "big nickel" package.

The 25-year-old will rely on that experience going forward, as he said Monday that he now knows the ins and outs of playing up close to the line of scrimmage.

"I think that's the biggest thing with any position — if you do too much thinking, then you're not really focused on what's going on around you," Kearse said. "Just me knowing what I have to do and doing my job, it makes it easier, as far as reading my keys. I'm seeing things quicker and much faster.

"Things happen quicker up there. I have to be in a run front much more than I would be if I was back deep at safety," Kearse added. "That's the biggest thing, just taking on those linemen and getting off of blocks."

Zimmer said Monday that Kearse is going to have help at times when it comes to coverage, but added the 6-foot-4 defensive back can present a different look with his size and physicality.

"I think, usually if he gets his hands on guys, he's pretty good, so that's part of it — using his length in that position," Zimmer said. "That's probably his strength, and that's what he needs to continue to do."

In the Vikings locker room Monday, Kearse talked about the challenges of playing in the slot at a height that is sometimes six inches taller than teammates or opponents.

Kearse said he's been focused on getting in and out of breaks smoothly so he can go up against against versatile guys.

"There's ways you can work on it. But it's a lot harder," Kearse said of being fluid in space. "It's easier said than done … compared to a guy like Mackensie, a guy who's like 5-10 or 5-11.

"It's just center of gravity. I'm a little taller, so it's a lot more difficult for me," Kearse added.

But it's something I've been working on — my lateral movement — knowing I wanted to be in this role."

Kearse handled the role just fine Sunday against Atlanta, racking up eight total tackles while primarily matched up against Falcons wide receiver Mohamed Sanu, who is 6-foot-2.

And when the Vikings defense lines up Sunday at Lambeau Field, they will go against a set a Packers wide receivers who are 6-1 and above. Green Bay has four receivers listed at 6-3 and above. Pro Bowl receiver Davante Adams is 6-1. (Packers rookie wide receiver Darrius Shepherd is 5-11, but he was inactive in Green Bay's season opener).

"You have the unique guys, like [Buffalo's] Cole Beasley, a little shifty guy … but you've also got guys like we just went up against. Mohamed Sanu, he's a bigger guy in the slot," Kearse said. "It's easier for me because he's a bigger guy.

"But when you go against these smaller guys, then it becomes a lot more difficult," Kearse added. "Over there in Green Bay, they don't have those short guys like that."