Marlon Mack admitted it was a little "bittersweet" to watch the Colts' backfield take off last year after he suffered a season-ending Achilles injury in Week 1.

Jonathan Taylor racked up 1,169 yards and 11 touchdowns. Nyheim Hines totaled 862 yards from scrimmage and seven touchdowns. Jordan Wilkins chipped in with 308 yards.

And Mack? Four carries, 26 yards before he was injured and missed the rest of the season.

"I just wish I could've contributed a little bit more, but on the sidelines I was watching from home doing the best I can," Mack said. "I just knew it was going to take off like it did."

Mack, who rushed for 1,999 yards and 17 touchdowns in 2018-2019, re-signed with the Colts as an unrestricted free agent this week. He said he's in "a good spot" with his recovery from that September injury and "should be good to go pretty soon."

The Colts were excited about the prospect of combining Mack, Taylor, Hines and Wilkins a year ago; with Mack back in the fold, the hope is the team can see just how dangerous that group can be in 2021.

"This is going to be crazy because once one guy gets hot, it doesn't stop because the next guy is going to do the same thing and the next guy – like all of us have that one-play thing," Mack said. "We all can take one play and it's going to pop for 60. So every team has to be on their toes because we are going to keep running and they have to be prepared for it."

Figuring out how to distribute touches among a deep stable of running backs may be a challenge — but it's a good challenge to have. Between Mack, Taylor, Hines and Wilkins, the Colts may have one of the NFL's strongest backfields in 2021. But what matters, Mack said, is the end result.

"I know coach Frank (Reich) – those guys are going to cook something good for us," Mack said. "I know it is only one ball but those guys are going to take care of each one of us. We know we are going to make it work."

"As long as we get to that one thing, that one main goal – that Super Bowl – I think we are going to all be good and happy with it."