It was less than four months ago, but the last meeting between the Chargers and the Jets seems like a faded memory. In their Week 2 matchup in San Diego, the Jets jumped out to an early 17-0 lead and cruised to an easy victory. Since that mid-September afternoon, so much has changed for both the Jets and Chargers that it seems as if this is a matchup of two completely different teams.

A year ago, the Chargers finished with the worst record in the league. Veteran head coach Marty Schottenheimer was on the hot seat, and the team entered the 2004 season with enough new personnel to make any rapid improvement seem unlikely.

All five starters on the offensive line were new, there were no proven players at wide receiver or tight end, and a contract holdout by first-round draft choice Phillip Rivers meant that incumbent Drew Brees – a guy they didn’t want back – had to return as the starting quarterback.

Add to that a defense that was struggling to learn a new system, and it’s easy see why expectations were pretty low in San Diego heading into the season.

By contrast, the expectations for the Jets were extremely high. A revamped defense boasted youth and speed. Chad Pennington was at full strength after missing the first eight games of 2003 with a broken wrist, Curtis Martin burst out to the best start of his career, and the Jets were looking at what seemed to be a soft early schedule.

But after the first 5-0 start in franchise history, Gang Green went 5-6 the rest of the way, suffering losses in three of their last four games. The offensive rhythm was lost when Pennington injured his shoulder midway through the year, and the defense revealed its vulnerabilities during the month of December. With Pennington showing unmistakable effects of the injury and the secondary surrendering big plays, the Jets limped into the playoffs as a team with too many question marks.

San Diego, on the other hand, overcame its slow start to win nine of its last 11 games, with the two losses coming against two of the league’s best teams – Indianapolis and Atlanta – by a combined total of four points. Brees rebounded from the brink of oblivion to win the Associated Press award for Comeback Player of the Year, as well as a Pro Bowl selection.

His favorite target, Antonio Gates, emerged as arguably the league’s best tight end. Defensively, the Chargers were able to master the 3-4 defense implemented by coordinator Wade Phillips and blossom into the league’s third-best run defense.

On paper, these two teams share many similarities and some key differences. Both have great running backs to help control the clock and sustain long drives. Both have an outstanding run defenses and vulnerable secondaries. The key difference between the two is at quarterback, and that’s the most surprising change since their September meeting.

Back then, the Chargers saw Brees as a failed prospect who was simply holding the job until Rivers was ready to step in. Maybe it was that lack of pressure that enabled Brees to finally put it all together. He’s always had adequate pocket presence and leadership ability, but last year his inaccuracy and poor decision-making led to turnovers and made him generally ineffective.

This year, he’s connecting on the short and intermediate passes with accuracy, which helps open things up to throw downfield – he’s thrown six touchdown passes of more than 50 yards this season.

The arc for the Jets’ quarterback this season has gone the opposite direction. Pennington has floundered rather than flourished since the Jets invested $64 million in him over the summer. He blanched at criticism that he couldn’t win a big game and struggled down the stretch with the bum shoulder. While the Chargers found a Pro Bowl passer in a player they had given up on, the Jets find themselves with serious questions about a guy that they thought was their franchise quarterback.

It’s not just the momentum that is on San Diego’s side heading into this playoff game. There are several reasons why this matchup is particularly unfavorable for the Jets.

The biggest problem is facing a good 3-4 defense, something that the Jets have struggled with all season. The balanced front makes it more difficult to attack, especially with the power running game the Jets like to employ. The defensive linemen tie up blockers and let the linebackers flow to the ball.

The Ravens, Patriots, and Steelers all shut down the Jets running game this year with their 3-4 attack, and the Chargers now play it as well as anyone. Nose tackle Jamal Williams does an outstanding job of disrupting the center, enabling linebacker Donnie Edwards to close down rushing lanes before they open up.

The 3-4 defense also allows a team to blitz aggressively, a tactic the Jets have had a great deal of trouble countering in recent weeks. After being sacked just eight times in his first 11 starts, Pennington went down nine times in back-to-back losses to New England and St. Louis.

Against the Steelers, the blitz led to interceptions instead of sacks, and that’s what the Chargers try to do. Their young, aggressive secondary finished third in the NFL with 23 interceptions. This makes them vulnerable to big plays, but with Pennington’s limited arm strength, it’s probably not something the Jets can take advantage of.

When these two teams last met, we all thought it was a matchup of two teams headed in opposite directions. It ends up that we were right, just not in the way we expected. Whether they win or lose this game, the Chargers will head into the off-season feeling pretty good about where they’re heading. The Jets, meanwhile, must win or face an unexpectedly tumultuous off-season.