An MRI showed Cardinals wide receiver Larry Fitzgerald sprained the MCL in his right knee in Arizona's 19-16 loss to Houston on Saturday night.
Fitzgerald was hurt when he took a nasty hit from Texans safety Eugene Wilson as he caught a 16-yard pass from quarterback Matt Leinart. Fitzgerald stayed in the game.
Cardinals head coach Ken Whisenhunt said the team will be careful with Fitzgerald over the next few weeks.
"I think we know what Larry can do," Whisenhunt told The Arizona Republic on Saturday night.
Fitzgerald is expected to be ready for the start of the regular season, according to Whisenhunt.
"They say they want to be careful with it so it doesn't linger and I'm ready to go for Week 1 at St. Louis," Fitzgerald told The Republic. "It's frustrating, because I was having my best camp as a pro."
Information from The Associated Press contributed to this report.