The Dallas Cowboys showed in their opener why preseason expectations can often disappear when the games are for real.

Two words: Quincy Carter.

While Houston didn’t do much on offense in its 19-10 upset of Dallas on Sunday night, the Texans did enough in their debut as a franchise. A long pass interference call set up one touchdown and a long TD pass from David Carr to Corey Bradford was misplayed by safety Darren Woodson.

Those things happen.

But Carter and the Dallas offense couldn’t reciprocate.

Their first seven possessions ended in six punts and an interception by Aaron Glenn. Carter didn’t complete a pass until the second quarter and finished 13-of-30 for 131 yards.

He wasn’t helped by the receivers. Rookie Antonio Bryant was badly outplayed by Glenn, one of the NFL’s better cover guys, and Dom Capers’ field position game kept the Cowboys bottled up.

“Now they can go back to Dallas and have a hard-knock life,” said Houston defensive end Gary Walker. “We ruined their season.”

The Cowboys’ offensive troubles start at quarterback.

Jerry Jones took Carter in the second round of the 2001 draft and threw him right in the fray. He played eight games and got better late in the season.

But Carter’s still not ready to lead a team to the playoffs, or even get it close. And he’s certainly not ready for the sophisticated schemes of the West Coast offense.

In the wings is Chad Hutchinson, who hasn’t thrown a ball in anger since leaving Stanford to play baseball for four years. Carter was a baseball player, too, and he had the benefit of two college seasons before joining the Cowboys.

Yes, the defense might carry Dallas to .500 or close to it. But to expect Carter to lead the Cowboys on a playoff run may be asking too much.

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High expectations: St. Louis entered the season as the Super Bowl favorite for the third year in a row. And Mike Martz remained Mike Martz late in the third quarter, eschewing a tying field goal on fourth-and-1 on the Denver 9 to go for it. Kurt Warner threw the ball into double coverage and the Broncos went on to a 23-16 win.

A couple of things to note:

l Defenses are starting to catch up to the Rams, playing nickel coverages most of the game and playing physical all game, as New England did to beat them in the Super Bowl. It helps that Martz keeps ignoring Marshall Faulk and the run (10 carries for 19 yards).

l Kurt Warner is a little tentative because the offensive line has problems, especially at right tackle, where John St. Clair, who spent two seasons at the end of the bench, is now the starter for the departed Ryan Tucker.

But some pluses:

The New Mile High Stadium (or whatever they call it) is a murderous place to play, particularly in an opener. Denver played its best game of last season there on a Monday night against the Giants.

Maybe the Rams will go 15-1. Their home opener is next week against those same Giants St. Clair against Michael Strahan, who had four sacks off Tucker last season.

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Spurrier’s debut: A lot of people seemed surprised that Steve Spurrier used Stephen Davis so much in Washington’s 31-23 win over Arizona.

Why? Davis is clearly the Redskins’ best offensive player, but he’s a running back. Spurrier isn’t supposed to like that breed.

But Spurrier’s a good “ball coach,” as he refers to himself. And he’s not stupid.

“How many times did he carry? Twenty-five? Thirty?” Spurrier said after Davis ran for 104 yards on 26 carries and caught seven passes for 46 yards. “Sometimes you can’t believe what you hear or read. Hopefully, we’re not going to do anything stupid to lose the game.”