FRISCO, Texas -- At the four practices open to the media during the Dallas Cowboys' organized team activities and minicamp, all eyes were on quarterback Dak Prescott.

And for good reason. The last time he was on a football field, his right leg was in an air cast because of a compound fracture and dislocation of his ankle. He had two surgeries. His rehab was intense, but what he did in spring practices would carry weight, especially after signing a four-year, $160 million extension this past March. There was nothing spotted in Prescott's performance that would suggest the ankle will be an issue when the season starts.

As important as Prescott's return will be to the Cowboys' success in 2021, so will the return of three offensive linemen who did not do much on-field work during spring practices: Tyron Smith, Zack Martin and La'el Collins.

And Prescott knows it.

"They're the most important, if you ask me," Prescott said. "From the time that I got drafted until now, this offense is built off of those guys. They're the three most veteran guys on this team, and that's for a reason. Those guys are walk-in Pro Bowl guys when they're healthy, future Hall of Famers. Just to have those three guys lead the five guys up front, everything starts with them. The run game, that allows the pass game to open up. When you have those guys back healthy, energized, it's special."

For all of the Cowboys' offensive glitz -- Prescott, running back Ezekiel Elliott and wide receivers Amari Cooper, Michael Gallup and CeeDee Lamb -- they will not be the same without Smith, Martin and Collins, who combined to miss 36 games in a lost 6-10 season in 2020.

Smith played in two games before undergoing season-ending neck surgery. Martin missed a career-high six games because of a concussion and calf injury. Collins did not play at all because of hip surgery.

Because of their significance to the Cowboys' line, all three were held out of the competitive drills in the offseason program. Instead, they worked mostly off to the side with the Cowboys' strength and conditioning staff. They lined up in drills that did not have an opposing defensive line, working on their pass sets and footwork.

"I'm loving the positive vibes. They look great out there," Dallas coach Mike McCarthy said. "Tyron, going off last year's experience, I have never seen him smile as much. A big part of it is he is healthy. He is pain-free. He looks great. LC looks great and the big man can run. ... We definitely are a different line when those two guys line up. There is no question about that. It will be great to have them out there on an individual basis [after] what they have gone through last year. It definitely makes our line, our whole process up front, move a lot smoother."

When McCarthy took the job in January 2020, the Cowboys had what was considered one of the best offensive lines in football. Then Pro Bowl center Travis Frederick retired and Smith, Collins and Martin were injured. The Cowboys were forced to use 13 different offensive line combinations a year ago.

It wasn't an easy task for the veterans to watch from the sideline.

"You see somebody rough up your quarterback, and me not being able to step in and calm that out, that was tough," Collins said. "Any time your team takes the field, and as a true competitor and you're not out there, it's always tough. But it really gave me something to look forward to when I came back. It just gave me a lot of motivation and everything that I need to just keep moving forward."

Added Smith: "Honestly, it just pushed us to be better and just know what we have to get done."

Smith has had a recurring neck and back issue for the past few years that caused him to lose strength in his left arm. He has not played a full season since 2015. Following the surgery last fall, he said he feels better.

"It's no longer a lingering injury or something I have to worry about," Smith said.

Collins' hip injury was an issue he had been dealing with over time. It affected his ability to work out last offseason, leading to more problems, such as added weight, as he entered training camp. He said he has dropped about 10 pounds and is moving fine now.

"To be honest with you, I'm just starting to feel like myself again," Collins said. "It feels good. I'm working overtime just with treatment and physical therapy to make sure this thing is right, and all the hard work is definitely paying off."

Martin, one of the best guards in the NFL since arriving as the Cowboys' 2014 first-round draft pick, moved to right tackle for a spell last season, proving adept in that spot as well, but his calf popped against the Washington Football Team and he missed the final five games.

When training camp starts next month, Martin is expected to be a full participant, along with Smith and Collins.

"That's definitely a big thing, getting our O-line back, getting a lot of guys we didn't have -- a lot of key guys, like Pro Bowl O-linemen, you know, La'el Collins, Tyron Smith, Zack Martin," Cowboys running back Tony Pollard said. "All three of those guys are big for us."