Trent Richardson has not inspired confidence in his time with the Colts. (Getty Images)

The Indianapolis Colts and running backs coach David Walker have mutually agreed to part ways, the team announced on Monday, after a season that saw the team finish 22nd in yards per carry, 24th in rushing touchdowns and 27th in Football Outsiders' rushing DVOA.

Since offensive coordinator Pep Hamilton came into the job, he has professed a wish to be a power running football team fairly consistently, despite the clear strength of the team being Andrew Luck and the passing game. The Colts did throw more often this season than in any other under the Luck-Hamilton regime, but when the offense staggered late in the season, Hamilton again reiterated his desire to base the offense around the run.

After the Colts struggled to run the ball through the first two weeks of the 2013 season, Indianapolis general manager Ryan Grigson elected to trade a first-round pick to the Cleveland Browns for Trent Richardson, who to that point in his career had been wildly ineffective. This despite overwhelming evidence building up over the last five years or so that running backs are eminently replaceable and not worth expending precious draft capital on. Richardson proceeded to carry the ball 157 times for 458 yards (2.9 per carry) in the 2013 season's final 14 games.

Despite his disastrous first two years, during which he averaged a total of 3.3 yards per carry on 455 runs, the Colts entered the 2014 season with the intention of Richardson being their starter once again. Indianapolis gave its running backs 337 carries this season, of which Richardson received 159. He totaled 519 yards on those 159 totes, an average of... 3.3 per carry, exactly what he'd averaged through his first two seasons. The remaining 178 running back carries were split between Ahmad Bradshaw, Dan Herron and Zurlon Tipton, who totaled 794 yards, an average of 4.6 per carry.

Walker also got good seasons out of various other running backs during his time in Indianapolis. Running backs not named Trent Richardson carried the ball 714 times for 3,030 yards (4.24 per carry) and 17 touchdowns in the last three seasons while Walker was the position coach. That group of players includes Bradshaw, Herron, Tipton, Vick Ballard, Tashard Choice, Donald Brown and Mewelde Moore, not exactly the most awe-inspiring crew.

Given these figures, it seems fairly clear where the brunt of the blame for the Colts' disastrous running game should lie. There's Richardson, who has been an abomination ever since he entered the league. There's Hamilton and Chuck Pagano, who insisted on being a power running team and continually feeding Richardson the ball despite mounting evidence that he was simply not equipped to be an NFL running back. And then there's Grigson, who traded a first-round pick for a running back who looked terrible for 17 games in Cleveland and has continued to be terrible in his 19 games with Indianapolis.

If anything, Walker showed his value to the team in the production he gleaned from Bradshaw, a cast-off from the New York Giants, and Herron, a street free agent who was cut by the Bengals before landing in Indianapolis, as well as the various other cast-off backs the Colts have used over the years. But the Colts have made the playoffs and advanced a round further in every season of the Grigson-Pagano-Hamilton regime, so they needed a different scapegoat. For the running game, the running backs coach fits the bill, even if it's not all that clear why he should be the one to go.