SAN JOSE, Calif. — Usually, the best offense is a great defense. But sometimes, it works a little bit differently than that.

In the moments after his team’s 30-21 victory against the San Francisco 49ers on Sunday, Patriots coach Bill Belichick credited his offense and its clock-munching drives with helping the defense.

Though New England had prepared for San Francisco’s dynamic Mike Martz-created offense for more than a week, when the game began the defense was having some problems that led to several big 49ers early plays.

But as the Pats’ offense did its work and mounted sustained drives, it gave the defense time to make the necessary adjustments, get on the same page, and start shutting down the Niners, something it didn’t do in its previous game against the Dolphins.

“I think we were playing on our heels,” Rodney Harrison said of the defense in the early minutes of Sunday’s game. “If you study film, you understand that [with] Mike Martz, you never know what he’s going to do. They could come out with a four-wide receiver package, a five-wide receiver package, or a regular, base ‘21’ personnel.

“Initially, we were trying to find our way and dip our feet into the water, testing the water instead of jumping right in. If you play football, you can’t test the water. You’ve got to go out there and jump right in and play very confidently. Once we settled down, I think we did a pretty good job of making adjustments and communicating.”

After giving up two quick touchdowns to the Niners with a short, touchdown-scoring possession by the Patriots in between, the New England offense remained on the field for four and a half minutes at the end of the first quarter, allowing defensive players to huddle with coaches on the sideline and figure out how they could best attack the San Francisco offense.

“There was some extra time to get on the sidelines and get some adjustments taken care of,” Harrison said. “It gave us the ability to calm down, because we were all over the place. With the offense controlling the possession time, it gave us the chance to calm down and get things together.”

Communication was paramount on Sunday, particularly as the Patriots unveiled a few new personnel packages. At times, the team went with two or even one defensive lineman, with a lineup heavy on speed including Harrison, Jarvis Green, Mike Wright, Jonathan Wilhite, Terrence Wheatley, Gary Guyton, Brandon Meriweather and Pierre Woods.

There again the offense came in handy. Once New England took the lead, the 49ers had to pass more, allowing the Pats to use the speed package.

“San Francisco is a team, with Mike Martz, that presents a lot of challenges offensively and I thought our players and staff did an excellent job preparing for that offense, the scheme and the players,” Belichick said. “I wasn’t perfect, but we made our share of plays. Everybody gets credit for that. The coaches did a good job and certainly the players are the ones that have to go out there and execute the plays. The offense certainly helped too by getting ahead, giving us a lead and making it harder for the 49ers to run the ball in the second half when time became a factor.”

The Niners ran just six plays in the third quarter, two on a drive that ended with Harrison’s interception, and then a three-and-out as New England built its lead. Though the Patriots scored only seven points in the third, they had a drive that took more than six minutes and had the ball for a nearly six more combined minutes, keeping the ball out of the hands of Niners quarterback J.T. O’Sullivan.

smanza@projo.com