FRISCO, Texas -- The Dallas Cowboys will be without defensive end Randy Gregory for "multiple weeks" after he suffered a calf injury in Wednesday's practice, according to coach Mike McCarthy.

It is possible Gregory could go on injured reserve, which would cost him at least the next three games. Right now, the Cowboys plan to replace Gregory from within their roster and not look for free-agent help.

The timing of the injury hurts with the Cowboys set to face Matt Ryan and the Atlanta Falcons on Sunday, followed by Patrick Mahomes of the Kansas City Chiefs and Derek Carr of the Las Vegas Raiders.

Gregory is tied with Micah Parsons for the team lead in sacks with five and leads the team with 20 quarterback pressures. He also has forced two fumbles and recovered one as he has emerged as a key player on defense after suspensions marred the early part of his career.

"I think he was probably one of our best players. You could make the argument probably one of clearly our best players on defense," McCarthy said. "Yeah, very disruptive. Our team and our defensive players feed off his activity and yeah, definitely feel for him. He's having a heck of a year. But he's back in there this morning and he'll attack his rehab just like he has attacked everything else."

The Cowboys have not had DeMarcus Lawrence since the season opener after he broke his foot in practice. He is likely a few weeks from returning. The rest of the full-time defensive line has accounted for 4.5 sacks this season; however, Parsons, a rookie linebacker who also has five sacks, has been used as an edge rusher at times this season.

Dallas can look to use Parsons more on the edge Sunday against Atlanta, however, it has only five linebackers on the 53-man roster.

"The game starts at noon on Sunday," McCarthy said when asked whether Parsons could see more time as a defensive end.

The Cowboys have Tarell Basham, Dorance Armstrong, Chauncey Golston and Azur Kamara on the 53-man roster, with Bradlee Anae, who was on the active roster earlier in the season, and Breeland Speaks on the practice squad.

"Right now I'm focused on the players that are here," McCarthy said. "We made some adjustments once learning the news after practice yesterday. So we feel good about our plan and we'll stay the course."

McCarthy said the injury occurred during one-on-one pass rush drills. Gregory is the third Cowboy to suffer a calf injury this season. Wide receiver Michael Gallup has missed the past seven games with a calf strain but will make his return this week. Quarterback Dak Prescott missed one game (two weeks with the bye week) with a calf strain.

McCarthy said Gregory's injury is similar to the one Prescott suffered.

"There's no pattern between the multiple players because you always look at how and where it happens," McCarthy said.