One day after Rex Ryan put his running backs on notice by saying "we left some yards on the field," the Jets signed RB Jonathan Grimes from the Texans' practice squad, a source confirmed.

Grimes is an undrafted rookie from William & Mary who impressed the Texans in training camp. In the preseason, he rushed 28 times for 130 yards, a 4.6 average. He was one of their final cuts and landed on the practice squad.

Grimes joins a crowded but unproductive backfield. Starter Shonn Greene, coming off back-to-back poor performances, is averaging only 2.8 yards per carry. Look for backup Bilal Powell (4.0 average) and possibly Joe McKnight to have an expanded role.

On Monday, Ryan gave a lukewarm endorsement of Greene, who's supposed to be the focal point of the Jets' Ground & Pound offense.

"We'd like to get him going more, without question," Ryan said. "We'd like to see him get that average up around over 4 yards a carry. Again, we'll see. We'll keep working at it and hope we can get some things going here."

The Grimes signing was first reported by the New York Daily News. The roster stands at 53. The Jets will have an opening when they put CB Darrelle Revis (knee) on injured reserve. He could be replaced by free agent DB Chris Carr, who is scheduled to arrive later this week for a tryout, a source confirmed. Carr has played for the Raiders, Titans and Ravens. Ryan has always been a fan of Carr, who was cut by the Vikings at the end of the preseason.

Interestingly, Carr attended Boise State a few years ahead of Kyle Wilson, who replaces Revis in the starting lineup.