Ben Bass (pictured above) took the field with his Cowboys teammates Tuesday afternoon for a practice session against the Oakland Raiders.

The defensive tackle then turned around and was escorted to the locker room before practice got underway.

The reason: a Cowboys team desperate for help in the secondary traded Bass to New England for cornerback Justin Green, a source said.

Green, who began his college career as a running back at Illinois before being switched to corner, spent most of last season on the Patriots practice squad. He was called up for two games but failed to register on the stat sheet.