DENVER -- As former practice squad wide receiver Kendall Hinton warmed up inside Empower Field at Mile High to start at quarterback Sunday for the Denver Broncos, the team's usual starting quarterback, Drew Lock, took to social media to apologize for a "mistake'' in following the NFL's COVID-19 protocols.

Lock, Brett Rypien and Blake Bortles, who was on the practice squad, were all removed from Saturday's practice and told to isolate after being designated as "high-risk'' close contacts to quarterback Jeff Driskel, who tested positive for COVID-19 on Thursday.

Lock admitted Sunday the quarterbacks had not followed the league's guidelines for masks when the quarterbacks had been in a meeting together.

"In a controlled and socially distanced area, we let our masking slip for a limited amount of time. An honest mistake, but one I will own," Lock wrote in a statement. "I sincerely apologize and I fully understand why these safety precautions are so important. Doing the right thing for a majority of the time is not good enough.

"I pray for my teammates' health, safety and success today. I look forward to getting back on the field next week. Go Broncos.''

Lock, Rypien and Bortles are not experiencing symptoms and have tested negative since they were last in a meeting with Driskel on Wednesday. Driskel's positive test result came back Thursday morning and he was moved to the reserve/COVID-19 list.

Sunday was the third game Lock has missed this season; he was out for two games (and the majority of a third) earlier this season with a right shoulder injury.