It ain’t easy finding work in the NFL as a 32-year-old running back — especially one with a history of concussions.

Two-time Pro Bowl selection Brian Westbrook is finding this out the hard way as his job hunt continues into Week 1 of the season.

On Tuesday Westbrook traveled to South Beach to work out with the Dolphins. And after his session, he was feeling pretty confident.

Hello Miami!!! Killed the Workout!!Tue Sep 13 12:18:13 via Twitter for BlackBerry®Brian Westbrook

Alas, it was not meant to be.

Workout went really well, looked like the 2005 Bwest!! But they need some other players right now so I’m headed back to the farm!!Tue Sep 13 15:20:04 via Twitter for BlackBerry®Brian Westbrook

By “some other players” you can bet the Dolphins meant “some younger players with a bit more tread left on their tires and far fewer knocks to their noggins.” (Or something along those lines.)

The Dolphins drafted Daniel Thomas in the second-round to be their starter this season, but the newly-acquired Reggie Bush outshone him in camp to grab the starting job. Thomas missed Monday’s 38-24 loss to New England with a bum hamstring, and the Dolphins can’t seem to decide if they want 31-year-old re-tread Larry Johnson around or not.

Following his March 2010 release from the Eagles after eight productive seasons in Philly, Westbrook landed in San Francisco where an injury to Frank Gore helped him amass 340 yards and four touchdowns on 77 carries. But the 49ers decided not to re-sign him.

There are a number of teams with backfield depth concerns — including the Dolphins and Rams — but no one seems willing to take a flier on Westbrook. Or 30-year-old Clinton Portis, for that matter. Among the elder statesman to land on new teams this fall:

Ricky Williams (34) — Ravens

Larry Johnson (31) — signed, released and re-signed by the Dolphins

Chester Taylor (31) — recently signed by the Arizona Cardinals, who lost rookie Ryan Williams for the year