It is not the same arm in which Sanders had the biceps tendon tear last season. He is scheduled to visit Dr. James Andrews on Wednesday to get a second opinion to help determine how long he will be out.
"There's definitely several different routes that he can go," team owner Jim Irsay told The Associated Press on Tuesday. "But it's way too early to say that he's definitely done for the season."
Sanders, the league's 2007 defensive player of the year, was injured on the Texans' first offensive series when a pass was deflected by Colts safety Antoine Bethea into Sanders' face mask.
Sanders left his feet and landed awkwardly on his arm.
Team president Bill Polian told his radio audience Monday night that he had not yet gotten the results of Sanders' scheduled MRI, and Irsay said Tuesday it still wasn't clear what was wrong.
"I really can't confirm that one way or the other, and I don't want to speak until we have all the information," Irsay said when asked if the biceps was torn. "It would be misleading to do anything different than that right now, but he will get a second opinion, and we'll have something from there."
Part of the confusion stems from the fact that Sanders did limited work during Monday's non-contact practice at the Colts complex. He ran with his teammates and did not appear to be wearing a heavy brace on either arm.
But visiting Andrews, who has performed surgery on Sanders in the past, likely isn't a good sign.
Sanders' career has been full of booms and busts.
The Colts took the hard-hitting safety in the second round of the 2004 draft despite him having a stress fracture in his right foot. Sanders missed 10 games that season because of the injury.
In 2005, Sanders started 14 times, earning his first Pro Bowl trip. A year later, Sanders missed 12 games with a knee injury but returned for the playoffs and was a key cog in the Colts' Super Bowl run. In 2007, a healthy Sanders started 15 games, made 132 tackles, was selected to his second Pro Bowl and was the NFL's defensive player of the year.
Irsay rewarded Sanders with a five-year, $37.5 million contract, $20 million of that guaranteed.
But since then, Sanders has been through pure misery.
He's missed 24 of 33 regular-season games with an assortment of injuries -- including a knee injury and the torn biceps that kept him out all but two games last season. And Sanders' career log now shows 48 games played, 49 games missed in seven seasons.
Coaches and teammates said Monday they were hoping for the best.
"He's had a few [injuries] and certainly it's something that you look at and say this guy needs a break every once in a while, but the fact of the matter is we still don't know the extent of the injury," coach Jim Caldwell said.
If he can't play, veteran Melvin Bullitt will return to the starting lineup.
Bullitt has been a key contributor as Sanders' replacement the past two seasons when he started 27 of 32 games and last season's Super Bowl. Bullitt replaced Sanders in the lineup Sunday, too, and his interception set up the Colts' first touchdown.
"They're like, 'Hey, you're up,'" Bullitt said, describing what the coaches told him after the injury. "That's about it."
Sanders wasn't the only injury update Indy provided Tuesday.
The team also announced that receiver Anthony Gonzalez, Indy's 2007 first-round pick, would miss Sunday's game against the Giants with a high ankle sprain.
Yet the bigger question remains Sanders and whether he'll play again this season.
"I think we want to thoroughly look at where he's at right now and evaluate that," Irsay said. "We're hopeful, but we really don't know yet. It's literally day by day."
Information from The Associated Press was used in this report.