FRISCO, Texas -- The Dallas Cowboys will be without Zack Martin for Thursday's season opener against the Tampa Bay Buccaneers after the six-time Pro Bowl right guard tested positive for the coronavirus and landed on the reserve/COVID-19 list.

Because of the return-to-play protocols, Martin will not be cleared in time to play, although he is vaccinated. A fully vaccinated player can return to play in five days if he does not have symptoms following two negative tests separated by 24 hours. An unvaccinated player faces at least a 10-day quarantine.

"He's frustrated obviously," coach Mike McCarthy said. "But, hey, this is the world we live in right now."

The loss of Martin is a huge blow for an offense that did not take a snap fully together in the preseason -- the Cowboys held out quarterback Dak Prescott because of a shoulder strain -- and will face a Buccaneers run defense that was the best in the NFL last season.

The projected starting offensive line -- Tyron Smith, Connor Williams, Tyler Biadasz, Martin and La'el Collins -- played just three series together in four preseason games.

With Martin out, Connor McGovern would start at right guard. He started eight games last season (six of which came when Martin was out because of injury). Collins is dealing with a stinger issue but has been cleared to return to practice Sunday, as will Williams, who has missed the past two weeks after a stint on the COVID-19 list as well.

Backup offensive lineman Brandon Knight has been classified as a high-risk close contact and has also been placed on the list, while wide receiver Noah Brown remains on the list.

The Cowboys have had nine players on the COVID-19 list so far, which is more than they had all of last season, when six players combined to miss seven games.

"I'm not going to generalize them all, but I think some of the symptoms have been more like a general cold," McCarthy said. "I think our guys have done a great job. As soon as they feel something they come in regardless of the time, and [trainers] Jim [Maurer] and Britt [Brown] have done a great job staying on top of it. As soon as someone feels something, we've been getting tested, so I feel our process is in order."

Players went through a testing period Sunday morning and held virtual meetings before arriving at The Star for practice. They will have virtual meetings after practice, and that will be the routine on Monday as well.

"The numbers are up in our society, so I think we understand what we need to do," McCarthy said, "and I think we're more rehearsed in the protocols and the adjustments, like we make an adjustment today with the team, it was pretty seamless."