Alex Collins' day opened on a high note. Unfortunately, it didn't end that way.

The second-year running back got the first start of his NFL career, and he was a big piece of the game plan against the rival Pittsburgh Steelers. But Collins left M&T Bank Stadium in a much different mood after the 26-9 loss to the Steelers, and he was hard on himself for his second-quarter fumble that led to a Steelers touchdown.

"I feel the fumble could have caused the momentum swing," Collins said. "Definitely something that I don't want to let happen again because I feel like I let my teammates down. I put this one on me."

Collins coughed up the fumble midway through the second quarter with the Ravens already trailing 13-0. The Steelers recovered the fumble at Baltimore's 28-yard line, and punched it into the end zone six plays later to go up 19-0.

The fumble was Collins' second in 25 carries this season, and Ravens Head Coach John Harbaugh traditionally has little tolerance for a lack of ball security. He kept Collins in the game after the miscue, but made it clear that the fumbling trend can't continue for the speedy running back.

"He's not going to keep putting the ball on the ground," Harbaugh said. "He won't get any more opportunities [if he continues fumbling] – the leash isn't going to be long on that. When you come in here and drop the ball however many times he has dropped it, I'm not going to tolerate it. I like him. He's a good kid and he makes plays, but he has to hold onto the football."

The miscue was part of the reason the Ravens found themselves in an early big hole, and it soured a game where Collins was otherwise a bright spot. Collins had nine carries for 82 yards, and his 50-yard run in the third quarter set up Baltimore's lone touchdown.

He's impressed the Ravens since getting called up from the practice squad two weeks ago, and he's consistently looked like the team's top ball carrier. He's averaging 8.24 yards per carry, and he's picked up yards in chunks more than either of the team's other running backs.

His focus now is to make sure he holds onto the football so that the Ravens keep him on the field. 

"If you dwell on it, you'll just keep making mistakes," Collins said. "I've got a job to do out there and my teammates are depending on me."

It's unknown if the Ravens will stick with Collins in the starting lineup or go back to Terrance West next week in Oakland. They've used a rotation of Collins, West and Buck Allen throughout the season, and they're looking for one of them to seize the job.

"I don't know what the coaching plan is, but I'll always be ready," Collins said. "I never know when my number is going to be called, but I always like to be ready when it happens."