Rex Ryan’s bread and butter is toast.

The defense just isn’t winning games for the Jets this season. The unit isn’t even coming close. It’s been Mark Sanchez and the offense to the rescue.

Last season, the top-ranked defense surrendered 20 points or more just five times through 19 games, including the playoffs. In the Jets’ 30-27 win on Sunday, the Texans became the sixth opponent to break the 20-point threshold this season.

What’s even more troubling is the fact Ryan and general manager Mike Tannenbaum beefed up that side of the ball in the offseason with the pickups such as Antonio Cromartie.

“Nobody’s harder on the defense then I am because our expectations are so high,” Ryan said yesterday. “That unit in particular, I expect so much of them. Guys make mistakes, but we have to eliminate them.”

The Jets’ defense gave up just seven points for three quarters against the Texans before imploding in the fourth. Houston had four scoring drives — two touchdowns and two field goals — in a 12-minute span, forcing Sanchez and Co. to save the day for the third straight week.

“Our defense played bad enough to lose,” safety Jim Leonhard said.

Meanwhile, opposing quarterbacks are playing well enough to win. The Jets have dropped from first to 16th in pass defense this season, partially due to a faulty pass rush.

On Sunday, linebacker Bryan Thomas had the team’s lone sack on Matt Schaub, which brought the team’s sack total for the season up to a whopping 13. Schaub threw for 254 yards without a turnover despite being hobbled by a knee injury.

“A lot of it was technique and miscommunication. Defensively, we have to be on the same page and we weren’t,” Thomas said. “At certain points, they were coming at us with different looks, and we know that, but it’s how we handled it that led to them scoring as much they did in the fourth quarter."

Also baffling for the Jets is the number of big passing plays that last year’s top-ranked defense has given up. Not only are the Jets giving up more yards on the ground this season, the plays as a whole have been of the highlight reel variety. The Jets can count 33 separate breakdowns this year where the other team has managed to go for more than 20 yards on a passing play.

Compare those numbers to 2009. Through all of last year, the Jets gave up 31 passing plays of 20 yards or more.

The air attack this season started in Week 3 when Miami’s Chad Henne shredded the secondary for 363 yards. The Jets blamed the poor effort on miscommunication in the secondary, and the same excuse continues to be used eight weeks later.

“I think we’ve been doing a better job in communicating as the season goes on and that there is improvement in the secondary,” safety Brodney Pool said. “But we’re still giving up those ‘chunk plays’ when we break down and give them a lot of yards on a big play.”

Now the Jets' offense is responsible for big plays of its own if the team wants to win. Sooner or later, though, the defense may have to help them out.

“We have to commend those guys [on offense]," Thomas said. "They really bailed us out.”