Another performance like it, and the NFL playoffs could be Patriot-free for the first time since 2002.

New England may need to win its final four games to have a chance at a postseason berth, a task coach Bill Belichick's team hopes to begin when it opens a weeklong West Coast trip by visiting the struggling Seattle Seahawks for the first time in 15 years.

The Patriots' offense was clicking going into the team's showdown with Pittsburgh in Foxborough on Sunday, with quarterback Matt Cassel coming off back-to-back 400-yard passing performances and the team buzzing after a 48-28 win in Miami on Nov. 23.

They were tied with Pittsburgh 10-10 just before halftime on Sunday, but that's when things started to go awry.

First, New England kicker Stephen Gostkowski missed a 27-yard field goal attempt that would have sent his team into the break with the lead, then the Patriots (7-5) turned the ball over five times in the second half en route to a 33-10 loss.

Matthew Slater fumbled a kickoff for one of the team's giveaways, but Cassel was involved in the other four, fumbling twice and throwing a pair of interceptions. He finished the day 19-of-39 for 169 yards without a touchdown.

"It's not about Matt Cassel," Cassel said. "It's about 11 guys on offense trying to get better."

That unit could be without Wes Welker on Sunday after the wide receiver took a vicious hit from Pittsburgh's Ryan Clark and missed the rest of New England's loss. Welker participated in practice fully on Wednesday, but hasn't been officially cleared.

The Patriots are now tied with Miami for second place in the AFC East, trailing the New York Jets by one game in the division and Indianapolis and Baltimore by a game each in the race for the AFC's wild card spots. Even worse, their 5-5 record in conference play could harm them as a tiebreaker.

Still, they will have the benefit of a relatively soft schedule the rest of the way. After facing the lowly Seahawks, they will spend the week in California before visiting 3-9 Oakland. They also host Arizona, which has struggled on the East Coast, before closing at Buffalo on Dec. 28.

"A couple of weeks ago, all the games became must-wins," running back Sammy Morris said. "Now it puts a little more emphasis on every game."

The Patriots may have a little extra help on Sunday with the addition of outside linebacker Rosevelt Colvin, a former New England standout who was signed by the team this week. He was added following the losses of Adalius Thomas and Pierre Woods to injuries and could be ready to suit up against Seattle.

"He's a guy that can definitely rush the passer," defensive end Richard Seymour said, "but we need everything right now. We need a pass rusher. We need run stoppers. So all hands on deck heading out to Seattle."

The defensive unit has struggled the past few weeks, as New England has given up an average of 31.7 points in the last three games, losing two of them. After Miami racked up 326 passing yards in the previous game, the Steelers ran for 161.

The Patriots have won at least one playoff game each of the past five seasons, compiling three AFC titles and a pair of Super Bowls over that span.

But they lost in the Super Bowl last season despite entering with an 18-0 record, and are trying to avoid becoming the seventh title game loser in the last eight years to miss the playoffs the following season.

"I am confident in the team," Belichick said. "We have had our highs and lows and we bounce back from those. ... There has been a good effort and good attentiveness to try to correct things, improve and get them right. I don't see any reason why that would change."

The Seahawks (2-10) are hoping for a major change from their recent results. Seattle has already lost five in a row for the first time since 2000, and it hasn't lost six straight since 1994.

Even with Massachusetts native Matt Hasselbeck back under center the last three weeks following a back injury, the Seahawks' offense has continued to struggle. Hasselbeck was sacked seven times in a 34-9 Thanksgiving Day loss at Dallas, as Seattle was held to single digits for the third time in the last nine games.

"Coach (Mike Holmgren) told us we had to be close to perfect to beat these guys," Hasselbeck said. "We haven't been close to playing like that all season."

In his 17th season as an NFL head coach, Holmgren has never lost 11 games in a season, while the Seahawks haven't dropped that many since going 2-14 in 1992.

It's been nearly as long since the Patriots have played a regular-season game in Seattle. New England lost 10-9 at the Kingdome on Oct. 24, 1993 - the only time the Patriots have played in the state of Washington since 1985.

They've only met once in the last 15 seasons, when the Seahawks lost 30-20 in Foxborough on Oct. 17, 2004.