The Buffalo Bills added a little more mystery to their ambiguous new defense in Thursday's preseason finale in Detroit.

The Bills' starters played a true, 4-3 front in the two series they were on the field.

The Bills have switched to a 3-4 scheme under Chan Gailey and defensive coordinator George Edwards. They have used a four-man line on most passing situations in preseason, which is commonplace for 3-4 teams. But this was the first time they showed a conventional four-man front with three linebackers this summer.

There's no doubt it was calculated to provide the Miami Dolphins, the Bills' opponent in the season-opener, something else to think about.

"We wanted to get that look out there so that teams have to prepare for it," said linebacker Paul Posluszny. "We could end up using it a lot. I don't know. But we needed to practice it in a game and get a feel for it."

The Bills' defense is a relative mystery heading into the season. Buffalo has been "vanilla" all preseason, employing very few blitzes with the starters. The 3-4 defense, with its emphasis on bigger bodies up front and the uncertainty of which players are joining the pass rush, is a dramatic departure from the 4-3 scheme the Bills played the past four years. The scheme of former coach Dick Jauron emphasized smaller, fast defenders.

So just like any team that's making a major scheme change under a new coach, the Bills are as unknown as they're ever going to be for Week One of the NFL season.

Gailey seemed to relish a question about the 4-3 look when asked about it after the team's 28-23 loss to Detroit.

"We'll probably play that quite a bit this coming year," Gailey said. "I think we could be back and forth amongst that a lot."

Was Gailey exaggerating about "quite a bit?" Who knows? It has become more fashionable the past decade for NFL defenses to become more multiple in their schemes.

New England is one team that switches to a four-man front more often than most 3-4 teams. New Orleans, a 4-3 team, sprung a 3-4 scheme on Indianapolis during long stretches of the Super Bowl in February. Still, most 3-4 teams stick to mostly the 3-4 front in normal down and distances.

It must be noted Miami's offense hardly will be in the dark when it visits Orchard Park on Sept. 12. After all, the Bills' Edwards worked as an assistant in Miami the past five years.

Meanwhile, Miami's new defensive coordinator, Mike Nolan, has been playing his own "vanilla game" this summer. Nolan has called just one blitz in four preseason games with his starters on the field. Like Edwards, Nolan has a long track record as an NFL coach, and both teams will be keeping past tendencies in mind.

In Detroit Thursday, outside linebacker Chris Kelsay put his hand on the ground as the right defensive end to join Dwan Edwards, Marcus Stroud and Kyle Williams on the four-man line. Andra Davis played middle linebacker. Posluszny and Kawika Mitchell were outside backers.

In the Bills' base, 3-4 defense, Edwards, Williams and Stroud play on the line. Kelsay and either Reggie Torbor or Chris Ellis play outside linebacker. Posluszny and Davis play inside backer.

It's not much of an adjustment, since the Bills have a veteran front that is used to the 4-3.

"It's a package we work on," Mitchell said. "It's good to mix it up. We've got the three linebackers who can do it, so why not? All of us have the experience to go back and forth."

"It definitely gives us flexibility," Mitchell said. "The package we have is pretty nice that we have out of it. It's good, if I can get on the field."

Mitchell is a good blitzer, but that has not been evident in preseason. Posluszny hasn't blitzed much. (He did blitz late on a play against Cincinnati, and the Bengals scored a TD on it.)

The Bills haven't put much variety into their pass-downs scheme, either. They have showed mostly a four-man rush, with Posluszny and safety Bryan Scott lining up at linebacker. Mitchell could play on third downs with Posluszny but we haven't seen much of that look.

"We've pretty much thrown everything out there that we've got," Mitchell said with a straight face. "I'll leave it at that."

mgaughan@buffnews.comnull