TrentWilliams wore pads and a helmet and even stretched with his teammates on Thursday. But the Redskins' starting left tackle was not able to participate in the main portion of practice.Williamssuffered a bone bruise on his right knee in the first quarter of Sundays lossto the Bengals. He also did not practice on Wednesday.Askedif Williams would need to practice on Friday in order to suit up for Sundays game in Tampa,Coach Mike Shanahan said: Not necessarily so. But you would like to seeimprovement.Weknew he couldnt go in practice, Shanahan said, asked if Williams attempted to participate.I dont have one set rule forpracticing Wednesday, Thursday or Friday in order to play," the coach added. "But at least my experience isthat if you dont get some practice in during the week, its hard to playwell.IfWilliams cant go, its expected that journeyman Jordan Black will start inhis place against the Buccaneers.