Watson, who had surgery to repair the kneecap, also will be limited in training camp when it begins in July, but the team expressed hope he would be ready for the start of the regular season.
Cardinals coach Ken Whisenhunt confirmed the incident on Tuesday to the Arizona Republic. Whisenhunt said that
Watson had worked out at the team's practice facility earlier last Thursday, went to work out again at a local health club, and slipped while on the club's treadmill, injuring his kneecap.
"The thing that's disappointing is that Gabe has shown such great progress and he's getting it," Whisenhunt told The Republic. "Just the fact that he was working to get himself in shape after he had done his workout here is a testament to him.
"One thing that's an advantage for him is that he's in such better shape at this point than he's ever been in, it gives him a much greater chance at getting back quickly."
Watson's backup is Alan Branch, who was the Cardinals' second-round draft pick in 2007.
"Alan is going through typical first-year player things in the offseason," Whisenhunt told The Republic. "Now the focus on him is going to be a little bit greater. Hopefully, that will force him to pick up the urgency, which he has shown signs of doing."