FOXBOROUGH, Mass. – The seemingly invincible Patriots have shown chinks in their armor the past two weeks, and the rest of the NFL has noticed.

How else to explain no-name Steelers safety Anthony Smith guaranteeing a victory over New England today in their AFC matchup at Gillette Stadium?

Such a boast would have been unthinkable the past two months as the 12-0 Patriots rampaged through their schedule. But after back-to-back escapes against the Eagles and Ravens, both of whom had losing records, New England suddenly looks vulnerable.

Patriots coach Bill Belichick admitted as much this week, saying his team’s performance the past two weeks “isn’t where we’re trying to be.”

Belichick was shocked to see the Patriots trailing in the fourth quarter in both games, and he wasn’t the only one. New England had trailed in the second half twice in its first 10 games, so to find itself in that position twice in two weeks was jarring.

“I hope we don’t make a habit of that,” Belichick said.

To be sure, the Patriots remain the class of the league and firmly on track to become the NFL’s only unbeaten team since the 16-game regular season was adopted in 1978. A victory today would make the Patriots the fifth team in league history to start a season 13-0, and – despite Smith’s guarantee – they have to feel good about their chances against the Steelers.

New England has owned Pittsburgh since the 1998 season, winning five of the past six meetings. Two of those victories have come in the playoffs, including the AFC title game at Pittsburgh in 2005.

Considering that history, not to mention the Steelers’ own recent troubles despite a 9-3 record, Smith seemed to be out of his mind by challenging the Patriots the way he did.

But with the way New England struggled on defense in the wake of standout linebacker Rosevelt Colvin’s season-ending foot injury and how their offensive line and Tom Brady looked human the past two weeks, it’s understandable why the league no longer seems intimidated by the Patriots.

After watching unheralded Eagles quarterback A.J. Feeley throw for 345 yards and three touchdowns and the Ravens’ Willis McGahee gouge them for 138 rushing yards and a score, New England does appear vulnerable. Just don’t expect any Steeler other than Smith to say as much.

“They’re still the team to beat right now, and we know that,” Pittsburgh running back Willie Parker said.

bhubbuch@nypost.com