SAN DIEGO - It seems like it was in another lifetime.

On Sept. 16, the San Diego Chargers headed into a rematch with New England, eager to atone for their epic playoff collapse against the Patriots eight months earlier.

The Chargers said they had more focus than they did in the January game. But the Chargers weren’t even competitive the second time around. They were schooled by Tom Brady and Randy Moss, made a bunch more mistakes and were routed 38-14 by a team fresh off the Spygate scandal.

A lot has changed in four months, mostly for the Chargers.

They’ll play the Patriots again in Foxborough on Sunday in the AFC championship game, with the winner going to the Super Bowl.

The Patriots are undefeated, needing two more wins for the NFL’s first 19-0 season.

The Chargers advanced by upsetting last year’s Super Bowl champions, the Indianapolis Colts, 28-24 on Sunday.

The Chargers will be big underdogs. That’s OK with them. After winning eight straight and 12 of 14, they know they’ve at least righted all those early season wrongs, including the ones on display in the earlier game against the Patriots.

“We’re a totally different team,” said two-time NFL rushing champion LaDainian Tomlinson, who expects to play after a hyperextended left knee kept him out of much of Sunday’s win at Indianapolis.

AFC championship game Patriots 21, Chargers 12 Pats hold off Chargers in frigid AFC title game Celizic: Super Bowl no gimme for Patriots Defense bends, doesn't break for Pats Rivers' right ACL was 'totally gone' L.T. fires back at Neon Deion's criticisms Expert: Brady demands perfection, gets it SN: Secret Service would love Pats' O-line   Slide show: Quarterbacks and their women Team pages:  Chargers  |  Patriots

“We’re playing differently and at that point that was the second game that we had had with the coaching staff and what not. Obviously it was a long time ago from Week 2, but it’s still going to be a heck of a challenge.”

The Chargers and their fans came into this season thinking they were an elite team. There was a lot to build on following an NFL-best 14-2 finish in 2006, even though there was that shocking playoff loss to the Patriots.

After looking less-than-stellar in an opening win against Chicago, the Chargers flat out tanked against the Patriots.

The Patriots scored on the game’s opening drive and never looked back. They raced to a 24-0 halftime lead while the Chargers floundered.

Novacek's picks Cardinal rule In what should be a tight, exciting game, Arizona will find enough 4th-quarter offense to beat Pittsburgh NBCSports.com

San Diego’s Philip Rivers threw for just 63 yards and had two interceptions in the first half. One of the interceptions was returned 65 yards for a touchdown by Adalius Thomas, one of the Patriots’ big free-agent acquisitions.

The Chargers were embarrassed, and it only got worse. They lost the next week at Green Bay, then blew a lead at home against Kansas City. The hometown faithful didn’t take the third straight loss well.

It turns out the Chargers needed a month to settle in with new coach Norv Turner and his staff, and vice versa.