Before Mike Harris underwent his physical Thursday on the eve of 2016 training camp, he was hopeful he'd be cleared to practice after missing the end of spring workouts due to what he called "a little head injury."

A day later, Harris was placed on the non-football illness list as head coach Mike Zimmer described his status as a "medical issue." On Saturday, the 27-year-old offensive lineman said he doesn't have a timetable for his return.

Harris elected not to disclose what's ailing him, but said he's confident he'll be able to resume his NFL career eventually. Though he isn't sure that will be this season.

"I'm going to keep it personal, man," Harris said. "I'm not going to go any farther than that. As soon as I get the clearance from my doctor, I'll be back out there. So, just number one, I'm taking care of my health. I'm going to be around training camp, still on the team. Still going to be supportive. Soon as I get the clearance, I'll be back."

Harris has started 22 games since the Vikings claimed him off waivers following final training camp cuts in 2014. He figured to be Brandon Fusco's top competition at right guard, where Harris started 17 games last season.

Asked how the illness came about, whether by injury or on its own, Harris elected to keep specifics to himself. He did say the issue started in June, when he was initially sidelined after a healthy start to offseason workouts.

"I can't say, I can't say, man," Harris said. "I just wish I was on the field. Just following the doctor's orders. As soon as I get that clearance from the doctors, I'll be back. It's not going to hold me down for my career, just a mild setback. I'll be fine.

"I'm just taking it day by day. Keeping my spirits high, everybody's been supportive with my teammates and coaches. I'll be fine, man, just have to stay positive. It's doctors orders, as soon as I get some clearance, I'll be back on the field. That's where I want to be. Hurts right now not being able to play, especially after starting last year."