How soon can Eagles find safety in Trae Elston?

YONG KIM / Staff Photographer Defensive back Trae Elson (right), shown chasing down Birds wide receiver Marcus Johnson while with the Bills during a preseason game last month, now plays with the Eagles, who claimed him off waivers on Wednesday. Four days after playing a dozen special-teams snaps for the Buffalo Bills Sunday at Carolina, Trae Elston was sitting in the NovaCare locker room wearing a No. 35 Eagles jersey and a puzzled expression.

“I just got here. I’m just trying to learn, man. Whatever the coaches tell me, I’m just trying to do it,” Elston said, when asked if he thought he could learn enough about the Eagles’ scheme to play any safety Sunday against the Giants. “They really…