With less than four weeks remaining before their Sept. 12 season opener, the Washington Redskins continue to have doubts about the two players competing for the starting job at left tackle.

As promised, Coach Norv Turner is giving 11-year veteran Andy Heck a chance to earn the job. But Heck won that opportunity not on the merits of his own play, but because of a mistake by Joe Patton that led to a sack of quarterback Brad Johnson in Friday's 20-14 preseason victory over New England.

Against New England, Patton either failed to hear or failed to execute a play that called for the offensive line to shift to the left. Instead, Patton shifted right, creating the opening that defensive end Greg Spires quickly exploited.

"Joe is having a good camp, but it is the consistency thing," Turner said today. "Obviously you can't have the type of play you had in the game. You give a guy a free run at the quarterback, and you're just asking for a disaster. We just have to solve that problem."

Patton has declined to comment on his demotion.

Heck is taking a measured approach toward the opportunity to start Friday against Buffalo. But he wouldn't have put himself through the rigorous work of preparing for his 11th NFL season, he said, if he didn't think he could be productive.

"I'm not ready to run away from this game," said Heck, who was released by Chicago in the offseason. "I'm not ready to concede the fact that while I probably would have been a backup in Chicago, they hired a younger, stronger, faster guy."

It's unclear whether Turner's demotion of Patton is intended as a motivational tool to spur a better performance or whether it reflects a belief that Patton, who will count $1.5 million against the salary cap this season (his fifth as a Redskin), has failed to demonstrate his worth.

While Turner showed zero tolerance for Patton's mistake, he has given second chances to others who committed gaffes last Friday. Rookie place kicker Jeff Hall missed a 23-yard field goal, and defensive end Ndukwe Kalu nearly cost the victory by drawing a 15-yard penalty for roughing the passer with seven seconds remaining. Both mistakes, Turner said, served as good lessons for the players involved.

As for Patton, Turner said: "He had a heck of a practice yesterday. He competed awfully well. I expect him to fight to get back in that spot."

More than at any position on the team, the situation at left tackle points out the difference between the Redskins of today and the Super Bowl champion Redskins that endure in fans' memories.

When Joe Jacoby played, left tackle was a position to be feared. But in recent years, Redskins officials have tried patching it together with a revolving cast of personnel. After last year's experiment with guard Brad Badger failed to produce results, Patton was re-installed.

While new owner Daniel M. Snyder is eager to do what it takes to upgrade the team, there are simply no desirable left tackles available, scouts say.

The dearth of top players is a function of the difficulty of the position, which requires strength, agility and quickness, given that the job entails fending off speedy pass rushers whose livelihoods depend on knocking down quarterbacks.

But smarts also matter.

"A good defensive lineman is going to set you up," Heck said. "He's going to come: Bull-rush, bull-rush, bull-rush. And when he figures he's got you braced up, he'll slip you inside. You've got to know this guy has bulled me a couple times, so I know he's going to beat me inside."

Heck points to Jacoby as the supreme example.

"I feel like there were better athletes out there on the football field," Heck said, "but very few played the position better than he did because he was, number one, enormous. But, number two, he also played with terrific technique and was a very smart player. For 13, 14 years in the league, he proved he was very accountable and durable -- all the things that make good offensive linemen."

Both Patton and Heck are slowed to some extent by chronic injuries.

Patton, 27, suffers from recurring bouts of tendinitis and missed five games last season. So far during camp, however, he has played through the pain.

Heck, 32, has a history of lower back problems, but it has not cost him practice or playing time over his 10-year career with Seattle and Chicago.

After being released by the Bears, Heck, a graduate of W.T. Woodson High in Fairfax, decided against retiring.

Instead, the former first-round draft pick went to the trainers for the Chicago Bulls to pursue a unique brand of therapy.

Through a combination of Olympic-style weight lifting and deep-tissue massage, the therapy eased the pain that was caused by a degenerative disk condition that eventually afflicts most linemen. While Heck acknowledges he is not the player he once was, he feels his experience at left tackle compensates for any leg strength he may have lost.

"There are lots of big guys out there that look like they could be terrific offensive linemen," Heck said. "But can a guy stay healthy? Be consistent? Is he not going to make the crucial mental error that is going to get somebody hurt? When you get down to it, there are really not many guys who can do it.

"I'm not looking past this year. But I figure if I'm going to come into a situation, I'm going to give it everything I've got."