LANDOVER, Md. —Could Marlon Mack make his 2018 regular season debut today?

The second-year Indianapolis Colts running back, who has been out since Aug. 9 after suffering a hamstring injury in the team's preseason opener against the Seattle Seahawks, is officially active for today's regular season Week 2 matchup against the Washington Redskins at FedExField. (See the entire inactives list by clicking here.)

Mack was able to return to the practice field last week in a limited capacity, and then was able to increase his participation each day in the practice sessions leading up to today's game.

"He looked good, he looked good," Colts head coach Frank Reich said when asked how Mack looked in practice this week. "You can just see Marlon (Mack) has got that quickness, that explosiveness. So he has really made good progress."

Mack certainly showed flashes of his potential last season as a rookie, when he ran for 358 yards and three touchdowns, while also catching 21 passes for 225 yards and another score as the backup to veteran Frank Gore.

He entered the preseason this year as the Colts' top running back in their new offensive system under Reich, but saw the likes of Jordan Wilkins — who started in last Sunday's season opener against the Cincinnati Bengals — and Nyheim Hines take advantage of their opportunities in his absence since suffering his hamstring injury.

Clark at left tackle

After suffering a setback with his own hamstring injury during Wednesday's practice, the Colts on Friday officially ruled left tackle Anthony Castonzo out of today's game.

The question from there: who would start at left tackle? Would it affect who starts at right tackle?

The likely answer: Le'Raven Clark gets the start today at left tackle, while Joe Haeg will start at right tackle.

It was the second time Castonzo re-aggravated his hamstring injury, which he originally suffered while working out on his own prior to the start of training camp. He was eventually able to return to practice during camp, but hurt his same hamstring again on Aug. 3.

After missing the rest of training camp and the entirety of the preseason, Castonzo was held out of last week's season opener as a precaution, but was confident he'd be able to play in today's game prior to re-aggravating his injury once again on Wednesday.

Reich considered it a "minor setback" for Castonzo this time around.

In other starting lineup news today, Hassan Ridgeway is expected to get the start at defensive tackle in place of Denico Autry, who is out with an ankle injury.