Stafford appeared Saturday on the reserve/COVID-19 list, which means a player either has taken a test that has come back positive or has been in close contact with someone who has been diagnosed with the coronavirus.
The Lions, in a statement released Tuesday, said Stafford never had COVID-19 and instead had a false positive test after two negative coronavirus tests last Tuesday and Wednesday. On Friday, Stafford took a test that came back positive on Saturday.
His following three tests were all negative.
"To be clear, Matthew does NOT have COVID-19 and never has had COVID-19 and the test in question was a false-positive," the Lions said in a statement. "Also, all of Matthew's family have been tested and everyone is negative."
Stafford was the first starting quarterback to go on the reserve/COVID-19 list and, at the time, the eighth Detroit player. Since then, tight end Isaac Nauta, starting slot corner Justin Coleman, Kenny Golladay,and Stafford have been removed from the list, leaving T.J. Hockenson, Jalen Elliott, Arryn Siposs and Amani Oruwariye on it.
The Lions are paying attention to false positive tests because they could cause a player to miss a game if they occur during the regular season.
"It's one of those things that are going to be questionable for sure, but at the end of the day, we knew coming into this that there were going to be situations like this," linebacker Jarrad Davis said. "It's just something that we have to hope the NFL and NFLPA can continue to work at to, I guess, knock things out, knock situations out that are going to come up like this.
"Yeah, this might be the first one that we've heard about, but I'm sure that there's more that are going to happen."
Stafford's wife, Kelly, posted a message to Instagram on Tuesday expressing frustration with the NFL and the effect the league's process had on their family. She said the period between her husband's initial positive test and Tuesday's announcement was "somewhat of a nightmare."
"Even after we knew it was false positive, our school told us they were not allowed back, I was approached in a grocery store and told I was 'endangering others,' my kids were harassed and kicked off a playground," Kelly Stafford wrote. "I was told I needed to wait in my car when trying to pick up food, and people closest to us had to get tested just so they could go back to work.. and that's just to name a few things.
"I don't blame these scenarios on any of the people directly involved.. I understand where they are coming from, but I do blame the NFL. I blame the NFL for not holding themselves accountable. These are people's lives and livelihoods that are in those results in THEIR test sites. Maybe we should be absolutely positive a person has covid before releasing that info to the world."