"The nature and severity of the injury to Bob Sanders' right arm remains unknown, but this much is known about the Indianapolis Colts' veteran safety: He was fit enough to participate in the team's light workout Monday.

When the players reported for their work-out-the-kinks session following Sunday's loss at Houston, Sanders was among them.

Players were not made available for comment after practice and the team offered little update on Sanders' injury, which occurred during the first quarter of the 34-24 loss to the Texans.

"Bob's injury is an arm injury," team president Bill Polian said on his Monday night radio show. "That's all I know."

The fact Sanders was on the field might be a positive sign, but isn't necessarily one. He was scheduled for a magnetic resonance imaging test sometime Monday.

"We'll know more later," Polian said.

Until then, the team waits. And hopes for the best with Sanders.

"My heart goes out to him," defensive end Robert Mathis said before practice. "Throughout his career, he's been a guy who just wants to play football and (been) unable to do that because of injuries. Just wish the best for him and hope he gets back ASAP."

Once again, Melvin Bullitt stepped in at safety when Sanders departed.

"Hopefully, it's something minor and he can get back out soon," Bullitt said.

Sanders, who was limited to just two games in 2009 because of a knee injury and torn left biceps tendon, started against the Texans. He was on the field for Houston's first series and part of the second.

It's difficult to ascertain when Sanders was injured.

On the first series, Texans wide receiver Kevin Walters delivered a crack-back block that contacted Sanders' right arm. Later on the same drive, Sanders came up to help safety Antoine Bethea with coverage on tight end Owen Daniels. Bethea broke up the pass near the goal line. Sanders leaped over them to avoid contact, tried to break his fall with outstretched arms and seemed to land awkwardly.

Sanders remained on the ground for a few seconds but stayed in the game. Bullitt replaced him on Houston's next series, with Sanders returning for two plays."