Von Miller said he’s been taking COVID-19 seriously “since Day 1.”

So when a strange cough prompted the Denver Broncos’ star pass rusher to get tested for the coronavirus this week, he didn’t know what to expect.

Two days later, the eight-time Pro Bowler and Super Bowl 50 MVP heard back from his doctor: He’d tested positive.

“I was shocked,” Miller said Friday on NBC’s "Today" show, as he explained his strict adherence to social distancing. “I’ve been here in Denver for about four weeks now. I’ve probably left the house four times. With all those four times, I never got out of the car.”

Miller said his symptoms started with “a simple cough” then “got worse.” He knew his asthma had prompted similar symptoms before and tried his nebulizer, which the 31-year-old uses before football games and practices. But Miller’s girlfriend insisted the cough didn’t sound normal. Miller realized his nebulizer wasn’t giving its usual relief.

“This time was different,” Miller said. “It didn’t work like it should.”

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He waited another day. But, given his asthma, Miller said his assistant urged him to get tested for the respiratory illness that has infected more than 660,000 Americans and killed nearly 29,000, according to data from John Hopkins University. More than 8,200 have tested positive in Colorado, where Miller has stayed since leaving his San Francisco training facility to abide by stay-at-home orders; 355 in Colorado have died from complications.

Miller said he’s feeling better, and his symptoms are mild. But he wanted to announce he’d received confirmation of a case so people “take this seriously,” as Miller posted to his Instagram story Thursday night after his agent Jody Branion confirmed his test result.

“Given the circumstances in the country right now, he feels it's worth letting people know that this is a real concern and not something they can take lightly," Branion told USA TODAY Sports’ Jarrett Bell.

Added Miller on Instagram: “It’s definitely FOR REAL.”

After a standout career at Texas A&M, Miller was selected second overall by the Broncos in the 2011 NFL draft. He’s since started 135 games for the franchise, racing to 106 sacks, 490 tackles and 26 forced fumbles while earning three All-Pro selections.

Last week, Miller was unanimously selected to the NFL’s all-decade team for the 2010s.

Miller is the second NFL player to announce a positive COVID-19 test result. Los Angeles Rams center Brian Allen and New Orleans Saints coach Sean Payton have also tested positive.

The NFL hasn’t officially delayed its season, which is scheduled to start in September. But it has moved spring business, including its 2020 draft next weekend, to fully virtual formats. Teams will also begin virtual offseason programs on Monday.

While the league publicly maintains it hopes for a full season without delay, USA TODAY’s Jarrett Bell reported Thursday on contingency plans including playing games without fans in attendance. Widespread and rapid testing will be imperative to restart in-person operations. The league has also said no team can reopen its facility until all 32 teams are legally able to return to work.

Miller doesn’t want the NFL to rush a return.

“Whatever is safe,” Miller said. “That would always be my first precaution, whatever we have to do to get things back to normal, that’s what we should do.

“We shouldn’t move too fast.”