Well, they'd better hope Richardson is up to that task, because the Colts are running out of options at this point.
Bradshaw and Richardson were added this year in an effort to bolster a rushing attack that ranked 22nd in the NFL in 2012.
*Through five games
To this point in 2013, the team certainly appears to be accomplishing that goal. Its running stats are up across the board compared to last year.
However, the players the Colts were counting on to lead the way are now either injured or have struggled this season.
Among players with over 100 yards
Granted, some of Richardson's problems can be attributed to learning a new scheme on the fly. With that said, though, third overall pick or not, Richardson is a player who gained only 3.6 yards per carry as a rookie with the Browns last year.
For his part, head coach Chuck Pagano told Albert Breer of NFL.com (h/t Kevin Patra) last week that he has no worries where Richardson is concerned:
(Richardson) is a between-the-tackles, hard-nosed, tough, rugged runner. And he's got 4.4 speed. So if he gets to the second level, and happens to break a tackle, he can take it the distance. And that's gonna happen. That'll come. He's a young player still. He's learning, and obviously making the transition coming over from Cleveland, being here now for three weeks.
Richardson responded to that vote of confidence by gaining 56 yards on 18 carries against the Seattle Seahawks. Seattle's run defense is stout, but Donald Brown was able to gain 37 yards on just six totes in the game.
In fact, whereas many thought that Richardson's change of scenery would be a shot in the arm of the second-year pro, it's Brown's play that has picked up.
Over the past three games, Brown has gained 127 yards on only 12 carries. It's a small sample size, but Brown is averaging over eight yards a carry in 2013.
Will that continue? Almost certainly not. Brown has gained over four yards a carry only once in four seasons. Of course, he's also averaged more than 3.6 yards every year.
Make no mistake, though. The Colts didn't pull the trigger on that trade for a part-time back. The offense of new coordinator Pep Hamilton is built around a power running game, and unless Richardson falls apart, he's going to see over 20 touches a game from here out.
Should Richardson continue to struggle, Brown will pick up a few more carries. However, the Indy ground game rests more or less solely on Richardson's shoulders now.
How many rushing yards will Trent Richardson gain in 2013?
Mind you, even if Richardson continues to plod along and the Colts' ground game falls back to the middle of the pack, Indianapolis still has more than enough working in its favor to win the AFC South—especially with the Houston Texans struggling.
The Colts have an opportunistic defense, an excellent stable of receivers and a phenomenal young signal-caller in Andrew Luck.
One more ingredient would go a long way toward establishing the Colts as a bona fide threat to win Super Bowl XLVIII: a ground game that can not only move the chains but also keep the ball away from the likes of Peyton Manning and Drew Brees.
With Bradshaw on the shelf, it's on Richardson to provide that ingredient.