WHY THE JAGUARS SHIFTED TO A 3-4 DEFENSE

Other than a little excitement during the preseason, the Jaguars' new 3-4 defensive scheme hasn't generated much else. The Jags rank 25th or lower in passing defense and points allowed. They're last in the league in sacks. But given the circumstances surrounding the club's switch from a 4-3 scheme - which was utilized through six of coach Jack Del Rio's seven seasons - to a predominantly 3-4 front, the Jags might not be too far behind the learning curve, as crazy that sounds. "We're still learning the scheme," linebacker Daryl Smith said. "But once we really get it down and play it like it's supposed to be played, we'll be all right." Del Rio revealed at the NFL combine last February that he planned to dabble with the 3-4 this season. At the time, the coach insisted the Jags would operate predominantly out of a 4-3 front. Then a series of injuries and revelations changed everything. "We had been experimenting with [the 3-4]," Del Rio said. "Before the season, we spent a lot of time knowing we were going to do some of it. How much from week to week, we'd see - we'd jump in, jump out [of it]. But definitely, we were gonna keep more of a 4-3 [scheme]." Then defensive end James Mincey suffered a sprained thumb in the preseason home opener against Tampa Bay, and was waived four days later. With Mincey gone, the Jaguars lacked depth at the position, leaving James Wyche as the club's only legitimate 4-3 backup end. Then in the regular-season opener at Indianapolis, defensive end Reggie Hayward suffered a broken leg in the second half of the Jags' 14-12 loss, and another 4-3 end went down. The Jaguars placed Hayward on injured reserve, ending his season two days later. And by then, the Jaguars realized that Wyche wasn't the player they hoped he'd be. So two days after placing Hayward on IR, the Jags waived Wyche, a seventh-round pick in 2006. The move left just one bona fide 4-3 defensive end on the roster, second-year starter Derrick Harvey, who is now a 3-4 outside linebacker. "Mincey getting hurt, Reggie [Hayward] getting hurt, and then [James] Wyche not really turning into the guy we thought he'd be - those were three ends that were in our plans," Del Rio said. "So all of a sudden, we had to go to more of what we were having as a change-up front. [It] became a more prominent front." A roster stocked with defensive end/outside linebacker tweeners played a significant role in the change, too. Rookie Julius Williams, Bryan Smith, and Quentin Groves have played primarily defensive end most of their careers. But all lacked the size of prototypical 4-3 ends, while possessing the athleticism to make the transition to 3-4 outside linebacker. Rookie outside linebacker Russell Allen, meanwhile, played the same position in both the 4-3 and 3-4 fronts in college at San Diego State. Still the club needed one last ingredient to make the mix of players work. "The thing that helped it happen was [rookie nose tackle] Terrance Knighton," Del Rio said. "Without a big nose, you can't do it. If you have a big guy like Terrance, it gives you a chance." Early returns haven't done much to confirm Del Rio's faith in the revamped scheme. But a closer look reveals the Jags aren't markedly different statistically after six games from the 2008 defense, which operated out of a 4-3 front. Criticisms of the new scheme seem to be the same as what was said about the old defense: - Can't rush the passer. The Jags posted five sacks through the first six games this season. In '08, the club made eight sacks out of its 4-3 front in the same span. - Can't defend the pass. The Jags have intercepted five passes and allow an average of 262 yards through the air. At this point a year ago, the club picked off six balls while surrendering 230 passing yards per game. - Can't get off the field on third down. Opponents have converted 42.6 percent of third down, compared to a 48.6 third-down conversion percentage last year in the first six games. Statistically, it's clear the 3-4 hasn't produced significantly different results than the 4-3 last season. But the Jags didn't become a full-time 3-4 defense until after Hayward's injury. So realistically, they have only five games of full-time experience in the 3-4. "I came here from a 3-4 team [San Francisco]. The 4-3 and 3-4 are two different styles," said defensive end Atiyyah Ellison, who joined the Jaguars last season as a defensive tackle. "I had to try to forget all that I had just learned and get back to a 4-3, like I played in college. Now it's the same thing again. But we didn't have the whole OTAs and offseason to learn how to play a 3-4. We were kind of just forced to take what they gave us." Del Rio hesitates to classify the defense as a full-blown 3-4, because he says the team still practices some 4-3 principles and ideally would like to play multiple fronts. Del Rio said at some point this season, the Jaguars will start operating more out of the 4-3. But until then, the Jags continue to try to master their new scheme. Five games isn't enough time to render a verdict because the Jags hadn't run the 3-4 at all before this season. "You do what you can with the guys you have. We expect it to keep getting better," Del Rio said. "Part of what we spent so much time in the offseason on was having flexibility. We're really just looking to put guys in the best position to do things we think they do well." michael.wright@jacksonville.com, (904) 359-4657 Jaguars DEFENSE, 2008 VS. 2009 THROUGH SIX GAMES 2008 First downs 3rd down % YPG Passing yards Sacks Int 20.1 48.6 340.3 229.6 8 6 2009 First downs 3rd down % YPG Passing yards Sacks Int 20.3 42.6 360.8 262.0 5 5 Jaguars AT Titans When: 4:05 p.m. Sunday -- Where: LP Field, Nashville -- TV: CBS -- Records: Jaguars are 3-3, Titans 0-6