An MRI exam on the injured right knee of tackle Trent Williams revealed a bone bruise, Washington Redskins Coach Mike Shanahan said on Monday, a better-than-feared outcome for a team that has been battered by injuries in the first three games of the season.

Shanahan said the third-year pro will be evaluated on a day-to-day basis and that his status for Sunday’s game at Tampa Bay remains uncertain.

“The MRI was negative. He’s still a little bit sore right now, so it’ll be a day-by-day evaluation,” Shanahan said.

Williams, who is charged with protecting quarterback Robert Griffin III’s blind side, injured his knee on the second play of the game. He tried to return twice but could not play.

“He came back for a little bit, and he actually did decent on one leg, but I don’t want him getting hurt for the whole season,” tight end Fred Davis said. “Losing him would be really bad. He’s a big factor. But this is the NFL. A week of practice, and somebody has to fill that void. Probably won’t be as good as Trent, but he’ll get the job done.”

Williams — whom Washington drafted fourth overall out of Oklahoma in 2010 — missed two games in both 2010 and 2011 because of knee injuries, but none of the injuries required surgery. He also was suspended for the final four games of 2011 for violating the NFL’s substance abuse policy.

In the event that Williams couldn’t play, the Redskins would probably start Jordan Black, who came off the bench to replace Williams in Sunday’s 38-31 loss to the Cincinnati Bengals. It was Black’s first action since Week 17 of the 2010 season.

The ninth-year veteran was out of football last season and earlier this summer figured he would retire. But after a rash of injuries along the Redskins’ offensive line during the first week of training camp, Black — who played under Washington offensive coordinator Kyle Shanahan in Houston in 2007 — received a call offering him a tryout.

The 6-foot-5 Black reported to Redskins Park weighing 270 pounds, and had to consume a 7,000-calorie per day diet to get back into the neighborhood of 300 pounds so he could hold his own in the NFL again. Black beat out second-year pro Willie Smith and fifth-year veteran James Lee for a spot on Washington’s 53-man unit.

Black struggled early Sunday, yielding a sack on his first play. But he gradually improved as the game went on, and helped the offense gain 313 yards in the second half.

Black admitted that he needed to shake off some rust, but was encouraged by how he played later in the game. He said he plans to prepare this week as if he will be starting.

“Regardless of whether I played or not last year, being on the sideline and all of a sudden having to run in there and play, it does take some getting used to,” Black said. “. . . For me, personally, it’s easier to go into a game knowing you’re a starter than it is going into a game watching on the sidelines. As far as that goes, for me personally, getting a week of practices, preparing for an opponent will be a help.”

Williams went down as he was engaged with a defender on a 12-yard run to the left by Alfred Morris. When the play came to an end, Williams lay on the ground in obvious pain, and after trainers tended to him, limped off the field. Williams was fitted for a brace in the locker room and returned to the game late in the second quarter. He also played three snaps to start the third quarter, but left the game for good as he struggled with his mobility.

Williams appeared to be in good spirits but did not speak to the media at Redskins Park Monday. He did move with a limp and wore a lightweight brace on his knee.

Williams briefly stuck his head in the locker room during the media availability session but turned and went to the trainers room instead. A short time later, Williams was sitting in the hallway with teammates, where reporters aren’t allowed to conduct interviews.

Asked how he was feeling, Williams smiled, nodded and said only, “I’m good.”

The Redskins managed to rush for 213 yards despite Williams’s absence. That total was the most produced by Washington since a 296-yard performance against the New York Jets in 2007.

But the Redskins allowed Griffin to be sacked six times for a total loss of 53 yards. He was hit another seven times and on more than one occasion was slow to get up.

Shanahan stressed the line needs to do a better job of protecting Griffin.

“You don’t want a quarterback taking as many shots as he did yesterday. That’s for sure,” Shanahan said.