Getting Matt Cassel comfortable in the pocket is one of the Patriots’ goals as they prepare for next weekend’s game at San Francisco.

The Providence Journal / Glenn Osmundson

The Patriots’ offense is a work in progress while Matt Cassel adapts to life as an NFL starter. And while the side of the ball responsible for scoring points gets it together, the defense may have been exposed as a less-efficient unit than it was previously thought to be.

Bill Belichick has rattled off an extensive list of things his team would be working on during its bye week, and the extra reps will hopefully go a long way toward curing some of what ails the Pats: third-down offense and defense, the run game on both sides of the ball, red-zone offense and defense.

It probably can’t all be fixed in a couple of days, but progress must be made.

As the Patriots are so fond of saying, it’s a team game. But last year especially, the prowess of Tom Brady and the offense helped out the defense tremendously. If the unit gave up a touchdown, chances were pretty high that Brady & Co. would be able to get it right back.

The question now is whether the defense can return to being the strength of the club that it was a few seasons ago, or whether it has been exposed.

Because the problem with Cassel being a “game manager” is that he can manage the game only if the score remains close. If New England gets down by more than seven points, Cassel can’t yet bring the team back.

Witness Sunday: Cassel was 15-for-20 passing in the first half, with all but one of the completions coming when the game was still close.

But Miami went up, 21-6, just before the half, and Cassel was just 4-for-11 the rest of the way before rookie Kevin O’Connell was put in once the game was clearly lost. O’Connell was 3-for-4 in his first action of the regular season.

Cassel should improve; it cannot be overstated how little live-game action he had before stepping in for Brady in Week One.

While he obviously saw a significant number of snaps in the preseason, every NFL player will tell you that preseason speed isn’t regular-season speed.

“Every rep I can get is valuable,” Cassel said this week. “With every look I can get and every defense I play against, I get more experience. We will just keep learning from each and every situation that comes up and try to get better.”

What is unknown is how quickly Cassel will improve, and how long it will be before he can make faster reads, faster decisions, and even better making the best decision in the shortest amount of time.

“When you go back to throw and you have the ball in your hands, you have certain things you’re looking at,” Belichick said. “You have to decide what is the best thing to do. Sometimes it’s situationally driven: third-and-5, you might make one decision, first-and-10 on the same pattern, you might make a different decision. Sometimes you want to make the safer throw or the situational throw, other times you have two downs left on the same play (and) you might want to take a shot down the field even though if it was third-and-5 it might be different.

“I would say all of those things play into it and that’s for every quarterback. Experience is experience, but like everything we do, we all still have to make decisions based on what the information is at hand and what presents itself at that particular point in time. You do it on what you think is the best thing.”

While Cassel tries to fine-tune his decision-making, the New England defense must get back to its red-zone efficiency and get off the field. After goal-line stands in each of its first two games, Miami was 2-for-2 in goal-to-go situations and 4-for-4 in the red zone.

And here’s a few interesting stats: the Pats lead the league in first-downs allowed, but are 31st in third-down conversions.

New England has worked on its own issues and is turning the page. Next chapter, San Francisco. The Pats are hoping it’s a must-read.

smanza@projo.com