Albert Breer of Sports Illustrated explained that Lions star quarterback Matthew Stafford tested positive for COVID-19 on August 1, though it wasn’t a case of him coming into contact with another positive person. Stafford had two negative tests beforehand, which complicates matters:

“Lions QB Matt Stafford did, indeed, test positive for COVID-19 (this wasn’t a case of being in close contact with someone sick). The test was administered on Friday, and Stafford was asymptomatic beforehand. That means that Stafford passed tests on Tuesday and Wednesday, before the positive came up and landed him on the reserve list.”

Breer added that Stafford now has to go through the process of being cleared.

“This is a reminder that these tests still aren’t perfect, and problems could certainly result with players being tested as consistently as they will (which, in my opinion, is the right way to do it, and something the players pushed for). For now, it’s manageable,” Breer concluded.

Dr. Jessica Flynn, from Boston Sports Journal, shared her thoughts on Twitter:

“Stafford tested negative on Tuesday, Wednesday, quarantined Thursday, and tested positive Friday. Possibilities include (1) false positive – contaminated sample or tiny amount of viral RNA present, too little to infect (2) true positive – viral load increased.”

Stafford was placed on the COVID-19/Reserve list for the Lions on Saturday. He is the highest profile player to make the list for the Lions and the first quarterback in the NFL to make the list this year.

Wide receiver Kenny Golladay, tight end T.J. Hockenson, cornerback Amani Oruwariye, punter Arryn Siposs and safety Jalen Elliott are also in Detroit’s COVID-19/Reserve list.