Jon Jansen left Redskin Park Wednesday afternoon with a pair of videocassettes tucked under his arm: more footage of New York Giants defensive end Michael Strahan, whom Jansen has been studying as if he's the sole subject of a final exam.

A rookie right tackle, Jansen faces a monumental test Sunday: blocking Strahan, one of the NFL's best defensive ends, when the Redskins face the NFC East rival Giants (1-0) at Giants Stadium.

Almost from the day the Redskins picked him in the second round of the draft, Jansen has been poring over footage of Strahan, hoping to learn his strengths and weaknesses for what will be their biannual matchups.

So far, the strengths stand out.

"He's quick and can make athletic moves," Jansen said. "But he also has good power. He's one of those guys [with whom] you've got to be ready for everything."

As for the advice Jansen has gotten from offensive line coach Russ Grimm, it is simple: "Just get ready."

Strahan is one of those rare defensive players capable of shifting a game's momentum on his own.

In the Redskins' 31-24, season-opening loss to the Giants in 1998, Strahan not only spurred a third-quarter rally, but also helped snuff out quarterback Gus Frerotte's tenure as a starter in Washington. Lining up across from right tackle Shar Pourdanesh, Strahan sacked Frerotte on the Redskins' opening drive. In the third quarter, he intercepted a pass intended for tight end Jamie Asher and returned it for a touchdown that gave the Giants a 24-10 lead. On the Redskins' next series, Strahan sacked Frerotte again. One play later, Frerotte was out of the game and the starting lineup.

"There's a reason he goes to the Pro Bowl," Redskins Coach Norv Turner said. "They're an outstanding defense, and they use him extremely well. The way they blitz, the way they go after people. . . . They get him isolated one-on-one a great deal."

Protecting quarterback Brad Johnson has been a priority this week for the Redskins as they prepare for their second division opponent in as many games. Johnson, who underwent two surgeries on his knees during the offseason, said he hopes the coaches will mix the team's protection schemes enough Sunday to keep the Giants off balance. The coaches also will give Jansen help with his assignment by having the tight end line up on Jansen's side or by keeping a running back in the backfield to help block Strahan. In the Giants' 17-13 season-opening victory over the Tampa Bay Buccaneers, Strahan often drew double- or triple-teams and was held to one tackle and no sacks.

"It's foolish to put one person over there and say, `That's taken care of,' " Grimm said. "I don't think anybody in his right mind is going to put a tackle over there and say, `Hey, you take care of 92.' "

Strahan, who stands 6 feet 5 and weighs 275 pounds, recorded a career-high 15 sacks last season en route to his second consecutive Pro Bowl. During the offseason, he signed a four-year, $32 million contract that makes him one of the NFL's highest-paid defensive players. He credits his former coaches, Mike Nolan and Earl Leggett -- now the Redskins' defensive coordinator and defensive line coach, respectively -- for the technique that has proven so effective. But Strahan's sack production has shot up since the two departed, from roughly 5 1/2 per season to 14 1/2.

Strahan credits that leap primarily to a looser defensive style that allows more leeway to improvise on the field, rather than follow a script.

"Mike Nolan runs a great defense, and I think Earl is the best technician in the league," Strahan said. "Here with Coach [Jim] Fassel, there's just a lot more freedom. If you see something, you have the opportunity to change the defense. With Mike, it's a little bit more structured. I don't think there's anything wrong with the way he runs it. If you run it the way he says, you'll stop them anyway."

Strahan is formidable against the run and the pass, with exceptional strength and good speed. But what makes him so difficult to block is his mental mastery of the position.

"There's a mind-game going on for him," said Nolan, the Giants' defensive coordinator from 1993 to '96. "He's not just out there banging heads like some guys do for 60 minutes. Every play, he's got a plan going into that play. Mike messes with you a little bit. He's not just thinking about third down; he's thinking, `Three downs from now, I'm going to be in a third down. And I'm going to get you ready for that down.' "

A six-year NFL veteran, Strahan isn't taking his matchup with Jansen lightly.

"I'm the one with everything to lose," Strahan said, "because if I don't come out and play well against the rookie, I'm labeled as a guy who's not that good of a player, whereas the rookie is labeled as a good player."

Strahan said he believes the Redskins have upgraded their offensive line. He points to new left tackle Andy Heck's experience, the acquisition of three-time Pro Bowl selection Keith Sims at left guard, center Cory Raymer's maturation and Tre Johnson's shift to right guard as strengths.

The line performed well in Sunday's overtime loss to Dallas. Running back Stephen Davis had a career day (109 yards rushing), and Johnson was sacked only twice, plays for which he shouldered much of the blame himself.

The 6-6, 302-pound Jansen was one of the Redskins' most pleasant surprises of the preseason. He easily won the starting right tackle position and gave the coaches the confidence to trade Pourdanesh and release tackle Joe Patton.

Said guard Johnson: "As far as offensive linemen go, since I've been here he's been the most prepared rookie -- including myself. A lot of guys come in with physical gifts. Physically I was ready. Physically, I was a beast coming into the NFL. But mentally, I didn't understand a lot of the nuances that maybe he understands. He came with a lot of technique."

Jansen has worked hard in practice, dueling most often with defensive end Kenard Lang. He takes coaching well and his job seriously. Sunday, he gets his first big-time progress report.

Said Jansen: "It's one that you take a look at after the game, and say: `Well, this is where I am as an NFL player. This is where I stand. And the next time I see him, this is where I need to be.' "