Rex Grossman welcomes the chance to fill in for Donovan McNabb on Friday against the Jets and prove he can still start in the NFL. (Photo: Associated Press)

When Rex Grossman followed offensive coordinator Kyle Shanahan from Houston to Washington earlier this year, he believed that at some point, he would have the opportunity to step in for Donovan McNabb as the team’s starting quarterback.

“I just didn’t know it would come this soon,” Grossman says.

Friday night when the Redskins face the New York Jets in their third preseason game, Grossman will be Washington’s starter since McNabb sprained his ankle last week against Baltimore.

McNabb is expected to make a full recovery by the season opener on Sept. 12. But for the time being, the Redskins are comfortable with Grossman under center, because given the fact that he’s actually more fluent in the offense than McNabb, and considering his previous body of work, the eighth-year veteran is well prepared.

“Rex has played a lot of years in the National Football League,” Mike Shanahan said. “He’s played in the Super Bowl, and I think we know what he’s done. He’s had a good week of practice and it will be a good test for him against this defense, which is very sophisticated with their blitz packages.”

Said center Casey Rabach: “We have confidence in Rex. He’s been a starter in this league, so he can go out there and get the job done.”

Grossman has looked good during the preseason. He had a strong game in the Redskins’ preseason opener, completing 11 of 18 passes for 140 yards and two touchdowns. The following week against Baltimore, Grossman completed 14 of 21 passes for 195 yards, but he did throw an interception while forcing a pass near the goal line.

The quarterback describes his confidence as extremely high, and says he is a better quarterback than he was a year ago when despite being two years removed from taking the Chicago Bears to the Super Bowl he generated little interest in free agency and then was a late offseason addition to Houston’s roster.

“I feel a lot more comfortable with the play calls, how they all work with all the coverages,” Grossman says. “So much better than last year. Last year I got thrown into the mix kind of just before training camp, but now I’ve had a whole year in the offense, watching Matt Schaub run it, a whole offseason in it, and this year with camp, so I just feel so much better.”

Grossman doesn’t have the resume that rivals McNabbs, having started a full 16-game schedule only once in his career. But because of his familiarity in the offense, Kyle Shanahan said his expectations for Grossman are just as high as if McNabb were starting.

“We expect whatever quarterback’s in there to do well,” the offensive coordinator said. “Just execute the offense, get the ball in the right spot. When we have a bad play, don’t make it a worse play. Survive the down and get on to the next one.”

The third preseason game is usually seen as a dress rehearsal for the regular season, and because the starters typically play longer than other preseason games, coaches use that extended time to get the best possible evaluation of how things will look when the games count.

Grossman sees every opportunity as a chance to compete and showcase his talents, but he admits that taking the field with the starters rather than the second team -- which would’ve been the case had McNabb been healthy -- is a greater opportunity. He also sees the game as prime preparation for if McNabb -- who has played a full schedule only four times in his career -- goes down later this season.

“I have high expectations. I want to be very efficient, score some points, run the offense the way Kyle wants me to, and move the ball up and down the field, avoid mistakes. All the things you do every game,” Grossman says. Any time you play, you want to play well, whether you’re starting or coming off the bench. But I’m excited to get this chance to play. That’s why I’m here. I’m not here to watch Donovan. I’m here to play and step in, in that role when I’m needed.”