The Steelers had a plan at running back last season, a plan that worked great until it didn't.

What they were initially after was on display at Bank of America Stadium on Sept. 21 at Carolina, when starter Le'Veon Bell carried 21 times for 147 yards and backup LeGarrette Blount carried 10 times for 188 yards and a touchdown. The Steelers ran the ball 34 times overall, gained 264 rushing yards and averaged 7.8 yards per carry on the way to a 37-19 victory.

All that changed on a Monday night in Nashville, Tennessee, and then ultimately what they came to lack was as obvious as it was impossible to overcome on Jan. 3 at Heinz Field against Baltimore.

With Bell injured and Blount released the day after the team returned from Nashville, the Steelers were down to Ben Tate, Josh Harris, and Dri Archer at running back. And on third-and-4 from the Pittsburgh 26-yard line with 8:10 remaining in regulation in their AFC Wild Card Game against the Ravens and the Steelers trailing, 23-15, their worst fears were realized.

Tate, who had been signed on Dec. 30 and who was playing for his third team in 2014, whiffed on his pass-protection assignment and then batted quarterback Ben Roethlisberger's hurried check-down attempt up into the air while attempting to catch the ball. The pass eventually was intercepted by Baltimore linebacker Terrell Suggs and the Ravens were in the end zone one play later and in command.

Heading into 2015, the Steelers still believe in the veteran-complement-to-Bell design, and they've identified former Carolina Panthers running back DeAngelo Williams as that veteran.

It didn't work out with Blount, because he eventually balked at that complementary role, a role that was reduced dramatically in favor of a Bell-or-bust approach following a 20-13 loss to the Jets on Nov. 9.

The Steelers eventually had planned to stop splitting the carries toward the end of the season all along. Blount's ineffectiveness in the Jets game and the Steelers' 6-4 record after the Jets game convinced the staff to resort to that alteration earlier than anticipated.

Blount lasted one more game (Nov. 17 at Tennessee) and was eventually released after he left the field prior to the end of the fourth quarter, apparently in protest of a one-snap, zero-carry night. And then Bell went down (knee) in the regular-season finale against Cincinnati, an injury that prevented him from suiting up for the playoff game against the Ravens.

Enter Williams, who has 6,846 career rushing yards and a 4.8 career average per carry but is coming off of an injury-plagued 2014 season that saw him carry just 62 times for 219 yards.

He's been brought in to share the load rather than carry it and to provide a steady, veteran presence. And unlike Blount, Williams arrives having spent his first nine NFL seasons with one team rather than bouncing around the league, and with no perceived character issues or splotches on his reputation.

Williams (5-foot-8, 210 pounds) will turn 32 on April 25. But he spent a significant stretch of his career in Carolina sharing the backfield load with Jonathan Stewart, and also of late with Mike Tolbert. Williams has averaged 159.1 carries a season over his nine-year career (Bell had 290 in 2014).

As for the rest of the depth chart at running back, Harris was signed from the practice squad on Nov. 18, and the undrafted rookie from Wake Forest spent most of last season impressing teammates and coaches with his practice-field habits, his practice-field grasp of the offense and his practice-field potential. Harris led the Steelers with nine carries and with 25 rushing yards in the playoff loss to the Ravens.

Archer struggled to find a productive role as either a return man or a specialty back, but the 5-foot-8, 173-pound, 2014 third-round pick still has what Chuck Noll once referred to as "beep-beep speed."

The upcoming draft is also said to be well stocked at running back, and the Steelers could choose to spend a mid-to-late round pick on this position as well.