The Vikings sent Kirk Cousins home from their practice facility on Thursday, after an illness caused the quarterback to miss their early afternoon walk-through.

Coach Kevin O'Connell said the team was still "working through" whether Cousins' illness could be COVID-19. If he were to test positive for the virus, he would have to quarantine for five days under NFL policy.

"We're still in the process of trying to go through all of that, make sure first and foremost, 'What are you feeling? What's going on?' " O'Connell said. "And then go through our in-house process to make sure that if it does end up being [COVID], we're on top of it, and if it's not, there's still some other stuff going around that we want to make sure we're being smart about the other [89] guys, coaches, everything in-house. [Executive player health and performance director] Tyler [Williams] and [head athletic trainer] Uriah [Myrie] and their staff, we've had a lot of dialogue about that so we'll be smart and deal with it day by day."

O'Connell did not say whether the Vikings planned to play their starters in Sunday's preseason opener against the Raiders, though he added Cousins could stay home from the game in Las Vegas if he isn't feeling well. Even if Cousins' health wasn't a question for the preseason opener, it seems likely he wouldn't play much.

"I've kind of had a plan in my mind, as far as playing time throughout the preseason for him," O'Connell said. "Obviously getting on the plane and doing all of the travel stuff anyway, regardless of how he currently feels, what will matter is when it's time to get on the plane Saturday and go. That's something smart that we'll be really cognizant of."

If Cousins does not play on Sunday, the Vikings' decision on a starting quarterback would reveal something about their depth chart, where Kellen Mond and Sean Mannion currently share the No. 2 spot.

On Thursday, the Vikings gave both passers work with the No. 1 offense. While Mannion found Justin Jefferson for several longer connections, Mond fumbled a snap, continuing an issue that has cropped up for him throughout camp.

Mond was with the Vikings' backups as part of a two-minute drill at the end of practice, and after Greg Joseph hit a 60-yard field goal to end the session, the second-year quarterback took part in a walk-through with the offense, as O'Connell talked to him between each snap.

Asked about O'Connell's message to him before Sunday's game, Mond said, "I think [it's] just, 'Go out, don't think, just react.' I know the offense; just go out, react, play ball and just have fun."

It seems likely the Vikings will have more clarity about Cousins' status on Friday. His absence Thursday meant more work for the two quarterbacks fighting to be his backup.

"I think the quarterback room, we all help each other," Mannion said. "It's a lot of hours in there together, and we were all together last season. We're all preparing in there together. Kirk's obviously the starter, and he's one that's going out there most weeks, but I really think we all try to help each other prepare. It's been like that since I first met Kellen."

Vikings' plans with starters still TBD

While the Vikings' starters don't figure to play much in the preseason opener, O'Connell wasn't ready to announce definitive plans on Thursday, saying he'll make decisions on an individual basis.

"As a coaching staff, we're really looking at it from the standpoint of, 'Who do we want to see play?' " O'Connell said. "Who do we need to see play in certain competitive situations that we ultimately can't duplicate and replicate out here in practice or next week versus the Niners?' We'll be smart with the group, but at the same time, there's some guys that we're really counting on this year that will be out there to get some live snaps and really start feeling a new role."

In position groups where players have to work closely together to make pre-snap decisions, like on the Vikings' offensive line, switching out starters could make it difficult to grade players fairly. "We'll definitely take that into account, because I do think that matters when you're talking about truly evaluating somebody for their potential role on our team," O'Connell said.

Davis, Ingram continue competition

Second-round pick Ed Ingram got more work with the Vikings' first-team offense on Thursday, continuing to rotate with veteran Jesse Davis at right guard on the starting unit. The Vikings started giving Ingram more work with the No. 1 offense on Wednesday after they returned from a day off.

"I was honest when I told you guys about [competition at] that interior guard position and really from the beginning, we would kind of let the process and the repetitions kind of play themselves out," O'Connell said. "Ed has earned the right to get some reps with those guys, Jesse's done a really nice job as well, so that healthy competition is, I think, what's going to make our O-line the best possible group that I'm looking for for this season."