FLOWERY BRANCH, Ga. -- When the Atlanta Falcons open their OTAs on Tuesday, all of the attention will shift to the middle of the offensive line.
Center Alex Mack is recovering from a broken fibula and they must also replace right guard Chris Chester, who started 32 games over the past two seasons before electing to retire.
The Falcons are a week behind most other teams because they were cited for excessive contact and had three OTA sessions taken away by the NFL.
Stability along the offensive line was the untold story about how the Falcons were able to become NFC champions and reach Super Bowl LI. The Falcons used the same starters in all 18 games last season.
Mack is expected to recover, but it will be an all-comers battle royale to replace Chester.
Rookie Sean Harlow, who was selected in the fourth round of the draft out of Oregon State, started making his case during the team's rookie minicamp.
The Falcons have little experience among the holdover candidates at right guard, and Harlow will get his chance to show he can handle the job.
The Falcons will get a better handle on Harlow's ability when they hold full-squad, full-contact practices during training camp. But practicing in shorts with limited contact will allow Harlow to get a taste of the demands placed on linemen in the Falcons' outside-zone blocking scheme.
The system requires linemen to frequently run horizontally to spread the defense and create cutback creases for backs, thus placing a premium on their conditioning.
"That's a habit a lot of us need to start learning," Harlow said. "A lot of us are used to 'drive-stepping' and playing with a base. It's a little different having to run and really just move and 'go, go, go' and cover people up. But I'm excited to learn new techniques and new philosophies and try to earn my spot."
It's not a completely new concept for Harlow. Over his final two seasons at Oregon State he played for coach Gary Andersen, who installed a spread-option attack that used zone-blocking techniques.
But the Falcons' rushing plays were outside zone a vast majority of the time under coordinator Kyle Shanahan the past two seasons and helped set up an excellent play-action passing game. New coordinator Steve Sarkisian also plans to use those plays as a staple of the offense.
Harlow will compete with Wes Schweitzer and Ben Garland at right guard. They have the advantage of time in the system - Schweitzer was drafted in the seventh round in 2016. Garland was signed from the practice squad in December 2015. But Schweitzer has played zero NFL snaps and Garland played 42 offensive snaps last season.
Harlow moves to guard after he played tackle at Oregon State. His size (6-foot-4, 303 pounds) and athletic ability aren't ideal for playing tackle in the NFL, but he could be effective inside.
Harlow didn't stand out during the agility drills at the Combine. But his 40-yard dash time of 5.15 seconds was eighth-best among offensive linemen, and his 30.5-inch vertical jump tied for third best.
By comparison, Schweitzer reportedly ran the 40 in 5.15 seconds and jumped 27 1/2 inches at the San Jose State pro day in 2016. Garland reportedly posted a time of 5.07 seconds and jumped 35 inches at the Air Force pro day in 2010.
Falcons head coach Dan Quinn said Harlow is a quick study.
"He had very good questions (at the rookie minicamp) as far as (football) I.Q. goes," Quinn said. "He was ready to go to the next level on some things (the first) night and (Friday). He was another one that came in with the intent of how hard he could go for it. I was very encouraged by him."