With the four-game suspension of Sammy Morris, the Dolphins are suddenly in the market for a running back. They were already thin behind Ronnie Brown and are now even more desperate to improve their corps. Tennessee Titans running back Chris Brown, who has been asking for a trade since the start of training camp, is the biggest name available. A handful of productive backs, including Ron Dayne of the Broncos, may be released on Saturday, when each team has to get to the 53-man limit.