FOXBORO -- It was less than three short months ago that many NFL pundits thought that Matt Cassel was going to be cut by the Patriots.

He was having a horrible preseason, and Patriots backups Kevin O'Connell and Matt Gutierrez were playing well.

It seemed as if he was history.

"It's funny to me," Cassel said following Sunday's game, "a lot of people cast me out and said, 'This guy isn't even going to make the team.'"

But the Patriots' coaching staff and his teammates believed in him, stuck by him, and now he is making history.

On Sunday, Matt Cassel did something that no Patriot quarterback had ever done. He became only the fifth quarterback in NFL history to throw back-to-back 400-yard games.

It's a remarkable feat for any NFL quarterback, especially for one who hadn't even started a game since high school.

But Patriots offensive coordinator Josh McDaniels knew that Cassel had it in him even before he was thrust into the starting lineup after Tom Brady went down with a season-ending knee injury in Week One.

McDaniels isn't the least bit surprised that Cassel is having a breakout season, but he said that Cassel will have to be at his best once again this Sunday when the Patriots battle the Pittsburgh Steelers.

That's because the Steelers not only have the best pass defense in the NFL, limiting teams to only 168.8 passing yards per game, but they have the best rush defense (66.5 ypg.), and the best overall defense, allowing only 235.4 yards per game. They are only allowing 14.5 points per game, which also ranks No. 1 in the NFL.

"Obviously, there aren't a lot of weaknesses," McDaniels said. "They execute it extremely well. They are very physical. They pressure you. They cover well and they try to force you into turnovers and negative plays."

New England coach Bill Belichick agrees.

"You see their defense ranked at the top of the league in just about everything: rushing, passing, points, third down, red area," Belichick said. "Nobody has gotten 300 yards against them, and about half of their possessions are three-and-out. They are really solid across the board. It is no one-man band. They are good at everything."

Cassel, who has been sacked an NFL-high 34 times this season, is hoping his offensive line can protect him on Sunday. Only the Philadelphia Eagles (39) have more sacks this season than the Steelers (37).

Both McDaniels and Belichick said that the Pats' offensive line is playing much better than it was at the beginning of the season. It allowed just two sacks against the Dolphins when Cassel threw the ball 43 times, and three sacks against the Jets, when Cassel threw the ball 51 times.

"I think for the most part we were OK, considering the number of times we threw the ball," Belichick said of the pass protection against Miami.

Pittsburgh's ball-hawking secondary has intercepted 11 passes so far this season (ninth in NFL), which will be another concern for Cassel, McDaniels said.

In addition, Pittsburgh has the top-ranked red-zone defense, allowing teams to score a touchdown only 34.4 percent of the time in the red area, and the Steelers are allowing teams to convert a first down on third down only 36 percent of the time (9th).

The key to victory on Sunday, both Belichick and McDaniels said, will be executing and taking advantage of the plays that Pittsburgh gives them.

"You are going to have to work for everything," Belichick said. "You are going to have to execute whatever play you run whether it is run, pass or play action. Whatever it is, it is just going to have to be well executed and if it's not, then you are probably not going to get much out of it. If it is sloppy, you will probably turn the ball over. We're going to have to have a real good game of execution offensively, whatever the plays are."

roblee@projo.com