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INDIANAPOLIS, Ind. – The talk has centered around Jack Doyle and how a hummin’ Indianapolis Colts offense will continue to hum without him.

And rightly so. The veteran tight end, who suffered a season-ending kidney injury Sunday against Miami, did a little of this, a lot of that for an offense that is tied for 8th in yards and is 4th in scoring.

But here’s another concern: will that offense remain vibrant without Marlon Mack?

The second-year running back is in the NFL’s concussion protocol and did not practice Wednesday. Players respond to concussions differently, but it’s worth noting of the five previous Colts who suffered a concussion this season, only one – linebacker Anthony Walker – didn’t miss at least one game after sustaining head trauma. And Walker benefited from having 10 days to recover after being forced out of the Oct. 4 game at New England.

If the trend continues and Mack is out, the Colts’ ground game is in the hands of rookies Nyheim Hines and Jordan Wilkins, and Jonathan Williams, who was signed to the practice squad Oct. 2. Williams was elevated to the active roster prior to Sunday’s game with Miami, but was inactive.

“There are going to be injuries and there are going to be guys that are bumped and bruised,’’ offensive coordinator Nick Sirianni said. “Chris Ballard and his staff have done a great job of having guys in-house ready or on our practice squad ready for if we do need them.

“Your hope is everyone stays healthy throughout the entire year, but that’s just not reality.’’

The Colts have been through this before. Mack missed the opener while recovering from a hamstring injury suffered in the preseason opener at Seattle, then missed three more games after sustaining an ankle injury in week 2 at Washington.

If the Colts follow a similar Mack-less game plan, look for Hines and Wilkins to divvy up the carries. In the four games Mack has missed, Hines had 29 carries for 92 yards and Wilkins 34 rushes for 114 yards.

For things to carry on as they have with Mack in the lineup, perhaps Wilkins steps into Mack’s void which would allow Frank Reich and Sirianni to continue to maximize Hines’ open-field, pass-catching skills.

“It doesn’t matter what my role is,’’ Hines said. “Every week I prepare like I could pass block 20 times or run the ball 20 times. I don’t know (Mack’s) status, but I just know I’ve got to be ready to go out there and play like I do every week.’’

Andrew Luck is in the midst of arguably the best stretch of his career – five straight games with a pass rating of at least 100; 16 touchdowns, three interceptions; 75.8 percent completions – and no one should dismiss the impact of a complementary rushing attack.

More to the point, no one should dismiss the impact of Mack. The Colts have averaged 4.8 yards per attempt and 139.1 yards per game in the seven games the 2017 fourth-round draft pick has played. In the four Mack has missed, the averages plummet to 3.7 and 67.0, respectively.

Somehow, some way, the Colts must maintain a semblance of balance without Mack, and that figures to be difficult against Jacksonville. In the Nov. 11 meeting at Lucas Oil Stadium, the Colts won 29-26 while being limited to 81 rushing yards on 23 carries.

“It’s what we have to do,’’ Reich said. “I think that’s part of our DNA, part of who we are. We believe that we have to and need to be balanced.

“We believe we have the guys on the roster who can do that.’’

That might include Williams, who’s with his fourth team in three years. He has appeared in 14 games, all off the bench, with 94 yards and one touchdown on 30 career attempts. The vast majority of his playing time came as a rookie with Buffalo in 2016: 37 carries, 94 yards, one TD. He had three carries for no yards in three games with New Orleans earlier this season.

“He shows that he is a powerful back,’’ Sirianni said. “He has good feet, good vision. I see that he has good hands out of the backfield.’’

You can follow Mike Chappell on Twitter at @mchappell51.