Matheny told reporters the following about his status:
"I had this stuff about a month ago. It's given me more empathy but also the urgency to understand that we can be really careful [and still get it]. This thing's for real. It's a real deal and we have to be on top of our game to protect each other.
"I did have symptoms. We knew. We had a family member test positive, so we knew even before the test because we had exposure, so my wife and I took off and we quarantined just the two of us. And it was just the way they said it might happen, about three days [after exposure], I started feeling it.
"But we laid low and quarantined and stayed away from people and it ran its course. Fortunately I've been tested with the right antibody and looking forward now to donating some plasma to help out however we can."
MLB players began reporting to team training camps this week to begin preparations for the start of the 2020 season July 23.
Not every player is with their team, however, as several have tested positive for the coronavirus. On Friday, MLB announced 31 players were diagnosed with COVID-19. MLB tested 3,185 people, including staff members, and 38 of them—or 1.2 percent—tested positive.
The Royals announced earlier Saturday that catcher Salvador Perez was one of the 31 players who tested positive for COVID-19.
Players who tested positive will be required to test negative twice in order to rejoin their teams for summer camp. During the season, there will be a coronavirus list, similar to the injured list, but players won't have to be on the list for a set amount of time.
MLB is playing a truncated season in 2020, as the coronavirus pandemic caused the scheduled start of the season in late March to be delayed. MLB and the MLB Players Association couldn't come to terms on a deal, but MLB Commissioner Rob Manfred implemented a 60-game schedule, and the players agreed.
Matheny, 49, said Saturday he spoke to some of his players about the dangers of COVID-19:
"I didn't tell all of them I'd been through it. But I did tell some. But I told them we're going to cover each other's back to take care of ourselves and each other. I think to be able to personalize it, for them to see with Salvy—'Hey, that's our captain [and he had it]'—that's the conversation you have with the guys. Many of them feel bulletproof, and they are very low-risk. But don't deny the risk of taking it home to somebody. ... Just take it seriously, that this thing is real."
Matheny is set to begin his first season as Royals manager. The former catcher managed the St. Louis Cardinals from 2012 to 2018, but he was fired during the 2018 season following a 47-46 start.
Matheny went 591-474 during his tenure and led the Cards to the playoffs in each of his first four seasons, including a World Series berth in 2013. Matheny never had a losing record in St. Louis.
He served in an advisory role with the Royals last season and was hired as manager following the retirement of Ned Yost.
Matheny is taking over a team that went just 59-103 last season and hasn't reached the playoffs since 2015, when it won the World Series.