IRVING – The Cowboys are close to trading linebacker Bobby Carpenter to St. Louis for offensive tackle Alex Barron in what would be a swap of disappointing first-round picks, according to multiple sources.

Carpenter, the Cowboys' No. 1 pick in 2006, became expendable when Sean Lee was drafted in the second round two weeks ago. Barron, the Rams' No. 1 pick in 2005, became expendable when Roger Saffold was picked in the second round.

The move would help the Rams fill a void at weakside outside linebacker in their 4-3 scheme, while Barron would bring the Cowboys an experienced backup with the ability to play both tackle spots. He is not viewed as a challenger to Doug Free at left tackle.

Before a trade can be finalized the players must undergo physicals, and Barron must sign a restricted free agent tender offer worth $2.62 million. Carpenter has a $1.895 million incentive payment coming in the last year of his contract, but that does not appear to be an issue in the trade.

Carpenter started one regular-season game in his four seasons but became a valuable member of the nickel defense in 2009. He was credited by the coaches with 48 tackles, two sacks, one tackle for loss, four quarterback pressures and a pass deflection last season.

Drafted as an outside linebacker, Carpenter was moved inside in 2007. He upset the coaches with a poor performance in a preseason game at Minnesota and didn't recover until last season.

In addition to Lee, the Cowboys drafted linebacker Jason Williams in the third round last year and will give them the chance to replace Carpenter in 2010. With St. Louis, Carpenter would have a chance to be a starter.

Barron, chosen one spot before the Cowboys took Marcus Spears in 2005, has been durable, missing two games in his career. He has started at left and right tackle, and started all 16 games last season at left tackle. His five accepted holding penalties were tied for the most in the NFL last season and his five false starts were tied for 16th. According to Stats Inc., he gave up 7 ½ sacks.

The Cowboys will start Free at left tackle after releasing Flozell Adams last month, but Barron would provide veteran depth at both tackle spots. Currently, Pat McQuistan, sixth-round choice Sam Young and Robert Brewster, who missed his rookie season with a pectoral muscle injury, are the top tackle backups.

The Cowboys are also looking at other moves. The team has given the agents for wide receivers Patrick Crayton and Sam Hurd permission to seek trade offers, but nothing has yet materialized.

With this trade, St Louis would have an all OSU LB core if Carpenter starts! Diggs, JL, Carpenter!