TEMPE, Ariz. (AP) Kevin Kolb was back at practice on Monday, no longer competing for the starting job for the Arizona Cardinals but as a backup NFL quarterback once again.

The team's workout was its first since coach Ken Whisenhunt announced Friday that John Skelton would be the starter for Sunday's regular-season opener against Seattle.

``It's disappointing, that's obvious,'' Kolb said after practice. ``But if there's one thing I learned in this league is it's full of surprises, so you just keep pressing forward. If you take time to sulk or feel sorry for yourself, you're going to get left behind and then your opportunity's going to pass you by.''

Just before last season, the Cardinals traded cornerback Dominique Rodgers-Cromartie and a second-round draft pick to Philadelphia to get Kolb, then signed the quarterback to a five-year $63 million contract extension, $21 million guaranteed. On March 16, Kolb got a $7 million payment for still being on the Cardinals roster.

Kolb arrived with fans and those within the organization believing they had the franchise quarterback Arizona had lacked since Kurt Warner's retirement following the 2009 season.

But Arizona got off to a 1-6 start, and Kolb was sidelined with a turf toe injury. While not spectacular, Kolb's replacement Skelton did enough for his team to pull off some close victories. Kolb returned and engineered a win over Dallas, but on the first series of the next game against San Francisco, he took a knee to the head for a season-ending concussion.

After the Cardinals won seven of their last nine to finish 8-8, Whisenhunt declared an open competition between Skelton and Kolb. Through offseason workouts, training camp and preseason games, neither player distinguished himself. When Whisenhunt finally announced his decision, Arizona was the last team in the league to have a starting quarterback in place.

What went wrong for Kolb?

``I don't know that there's one thing,'' he said. ``My thinking of the deal is you just work as hard as you can possibly work, put in the time. I know there's still things to come here. I tell you all that every time something bad happens, and that's the perspective that I'll keep.''

The situation is familiar to Kolb. In 2010, he emerged as the starter for Philadelphia when the season began, but was injured and replaced by Michael Vick, who held on to the job when Kolb returned to good health.

That experience, Kolb said, taught him to be ready no matter what.

``When I was in this position before with Vick, I think it was three weeks later he went down,'' he said. ``Again, there's no time to sulk, no time to feel sorry for myself. I've just got to go back to work today and be ready for the Seahawks. It will be a big game for us.''

Skelton, who had called the competition between the two a friendly one, said he and Kolb had not talked about the outcome.

``We kind of just left it at that,'' Skelton said. ``We both are professionals about it. We both knew going into it the ramifications of it and everything, and I think it was best left unsaid.''

Arizona's star wide receiver, Larry Fitzgerald, seemed elated when the Cardinals traded for Kolb. The deal was considered a big reason Fitzgerald signed an eight-year, $120 million contract.

But when asked Monday about what had happened to Kolb in his brief, unhappy time in the desert, Fitzgerald said, ``That's the NFL. It's a tough business.''

``He works hard every day. He's here. He's committed to the cause,'' Fitzgerald said. ``He's done everything you can ask for for us, as a teammate. It's just unfortunate.''

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