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MIAMI (CBSMiami) -- Miami Dolphins rookie running back Jay Ajayi, drafted in the fifth round of the 2015 NFL Draft, suffered another setback at a critical time.

According to the Palm Beach Post, he suffered a broken rib during last night's breakout performance against Tampa Bay in the Dolphins' preseason finale, a game in which he rushed for 66 yards on nine carries.

With the Dolphins needing to cut from 75 to the final 53 by Saturday at 4 p.m., Ajayi is still expected to remain on the active 53, with the Dolphins "not believed to be considering him for the injured reserve list."

Ajayi has been battling for a spot in a crowded backfield, led by Lamar Miller and Damien Williams.

Be sure to check out our FinsOn4 Live Dolphins Blog where we will be posting season-long coverage, updates, photos, video, commentary and more throughout the entire 2015 season.