INDIANAPOLIS —By season's end, the 2017 backfield for the Indianapolis Colts was essentially a two-horse show, featuring a future Hall of Famer showing the up-and-coming rookie how it's done in the NFL.

That veteran presence, Frank Gore, continued his ground-and-pound assault on the NFL's all-time record books in his 13th year in the league. Items of note included:

• Gore is now fifth on the NFL's all-time rushing list with 14,026 yards. He can surpass Hall of Famer Curtis Martin to move into fourth place with just 76 more rushing yards. In 2017 alone, he passed a trio of Hall of Fame running back son the list: Eric Dickerson, LaDainian Tomlinson and Jerome Bettis.

• Gore is now just one of five players in NFL history to surpass 14,000 career rushing yards, joining Martin, Barry Sanders, Walter Payton and Emmitt Smith — all Hall of Fame inductees.

• Gore reached 1,200 yards from scrimmage in 2017, extending his NFL-record streak to 12 seasons.

At the other end of the spectrum was 2017 fourth-round pick Marlon Mack, whose milestones were filled with firsts across the board, including his first rushing touchdown in the season opener against the Los Angeles Rams, which was also the Colts' first touchdown of the 2017 season.

Here's a review of the play of the Colts' running backs in 2017.Gore-geous effort
The burst, physicality and relentless approach to preparation and playing were remained for Gore in 2017, as he led the Colts in rushing for the third consecutive season.

His third year with the Colts featured 961 rushing yards on 261 carries for three rushing scores, and through the air he added 245 yards on 29 catches with one touchdown — a highlight-reel, contested dive against the Baltimore Ravens in Week 16.

After wrapping up the season with a win over the Houston Texans, Gore — a free-agent-to-be this offseason — remained positive and continued to show his leadership.

"That was the right thing to do," he said. "A tough year and a lot of things didn't roll our way and a lot of close games. I wish we were getting ready for next week. I will say this group of guys (is) special. I take my hat off to all the young guys. They keep fighting, even these last couple when we are out there just playing to finish strong for our coaches. I am very proud of this group."Mack-knife
Mack was targeted for his slashing-style with home run ability anytime he got his hands on the ball, as attested to by Colts general manager Chris Ballard upon selecting the back out of the University of South Florida.

"At the end of the day, we went with Marlon just because of the speed and the explosive playmaking ability," Ballard said during the 2017 NFL Draft.

As Gore's understudy, Mack toted the rock 93 times for 358 yards and three touchdowns. He also added 21 receptions for 225 yards and a score, as well as three kickoff returns on special teams with a 23-yard average.

In the Colts' Week 5 victory over the San Francisco 49ers, Mack put his burst on display. He averaged 10.1 yards per carry, including a 35-yard glide around the right edge in overtime to help set up Adam Vinatieri's 51-yard game winning field goal.

Having served as an apprentice to Gore — and developing a close friendship that included enjoying Thanksgiving dinner with the rookie's family — the focus now is on how Mack can take what he's learned and apply it into his first full NFL offseason.Other notes
Before suffering a season-ending elbow injury Week 6 against the Tennessee Titans, Robert Turbin continued to establish himself as one of the top third-down backs in the league. Already a solid blocker, the 5-foot-10, 216-pound bruiser was Mr. Automatic in critical third-down-and-1 situations, as his 12-for-12 conversion rates in those scenarios since 2016 led all NFL players.

Turbin, who finished his season with 23 carries for 53 yards and a touchdown on the ground — as well as nine receptions for 56 yards — is set to return to the Colts in 2018.

Matt Jones and Josh Ferguson were the only other two running backs to get carries for the Colts in 2017. Jones, a waiver wire pickup prior to the regular season from the Washington Redskins, was often shuffled to and from the roster or practice squad throughout the season, and carried the ball five times for 14 yards. Ferguson, a second-year back out of Illinois, had one rushing attempt for five yards and three receptions for 16 yards, while also serving as a kick returner option.Number to remember
22: The Colts ranked 22nd in the NFL in rushing offense in 2017, averaging 103.8 yards per game. One would imagine this will be a huge point of emphasis for Ballard and the team's new head coach this offseason heading into the 2018 regular season.

---------------2017 Colts Review:
• Quarterbacks
• Defensive Linemen
• Running Backs
• Inside Linebackers
• Tight Ends
• Outside Linebackers
• Wide Receivers
• Cornerbacks
• Offensive Linemen
• Safeties
• Special Teamers