INDIANAPOLIS -- Florida, a school that's less than 200 miles from where he grew up and who he rooted for, didn't want him. Michigan offered him a scholarship, only to pull it later. Louisville joined the recruiting party too late.

That was fine with Indianapolis Colts rookie running back Marlon Mack. He had his sights set on the University of South Florida. That was the school that recruited Mack first and "loved" him the best throughout his high school years.

Mack showed his loyalty to the school by starting every game he played and left USF as its all-time leader in rushing yards (3,609) and touchdowns (32). Now he's showing the flashes to potentially be the most explosive running back that Andrew Luck (once he returns) has played with since joining the Colts more than five years ago.

Mack, after dealing with an assortment of injuries in training camp and early during the regular season, had the breakout game that many had been waiting for when he rushed nine times for 91 yards and a touchdown against the San Francisco 49ers on Sunday. His 22-yard touchdown run was the longest by a Colt since Week 16 of the 2015 season.

Mack added to his successful afternoon with a 16-yard run and his 35-yard run in overtime put the Colts in position to win the game. His performance earned him one of ESPN’s Unsung Hero honors for Week 5.

"The [run] in overtime was really just me using my vision and going outside and bouncing it," Mack said. "The other two were designed for me to go outside and some of them were designed for me to go inside. But on the one in overtime, I did it on my own, just took a chance and went out there and used my speed."

It's been a struggle for years for the Colts when it comes to finding a consistent running game. Frank Gore became the first Colts running back to rush for at least 1,000 yards in a season since 2007 when he ran for 1,025 yards last season. The Colts have only had a player rush for at least 100 yards in a game three times since selecting Luck in 2012.

Mack, given the opportunity, has the speed to join the list of 100-yard rushers. And based on coach Chuck Pagano's comments earlier this week, the fourth-round pick should see an increase in his workload in the backfield that also features Gore and Robert Turbin. Gore is still the team's primary running back, while Turbin excels in short-yardage situations.

"I think it'd be wise to try to find ways to get him the football and get him more involved," Pagano said about Mack. "I think that would've happened by itself had he been available the entire time. Marlon is a change-of-pace guy, he's a speed guy. He's an edge guy. When he gets outside on the perimeter he's dangerous, and we all saw that."

Mack didn't spend his youth growing up in Sarasota, Florida, watching the NFL -- even though he's a fan of Jamaal Charles. He watched the Florida Gators because of the way they played. He talked about watching the speed of former Colts running back Chris Rainey and former NFL receiver Percy Harvin while they played with the Gators.

Mack has only 25 carries this season, but it should be noted that five of those attempts have gone for at least 11 yards. The big chunk plays eliminate the Colts having to worry about long, mistake-free drives, something they've struggled with this season, especially when it comes to penalties. Mack is also a threat out of the backfield in the passing game.

"If people have to go the long, hard way and they've got to execute seven, eight, nine, 10 plays -- they’ll find a way to shoot themselves in the foot," Pagano said. "We try to avoid it, but it's hard. A guy jumps offsides, false start, muffed snap -- there are so many things. But when you can get a 20-yard play, a 40-yard play, it's the difference in ball games."

Remember Mack's 25 rushing attempts this season?

Eleven of those carries ended in no gain or a loss of yardage. He managed to get the majority of his yards on the edges. He'll have to show that he can run in the interior because teams aren't going to always let him get to the edge.

He also has to do a better job in pass protection. Mack said he only had about five protections he had to know while at South Florida. He has to know many more than that with the Colts. That's two of the reasons why it's unlikely that he'll become the starting running back at some point this season.

"I think that's the toughest thing for young backs to pick up and learn," Pagano said. "Having missed some time, he's missed time on task. Classroom is one thing. He's been in the classroom, but until you actually go out there and you're seeing it live and you're executing it live in practice, it's difficult. It's not easy. Even 13-year veterans have miscues at times because defenses present you with a lot of different looks and variations, especially on third-and-long situations."