"He was able to throw strikes with every pitch that he has," catcher Kevin Cash said. "He even broke out his changeup, which he doesn't use that much recently, and it was pretty effective for him. When you can get that cut fastball into lefties and then get ahead with his fastball down and away to righties, he's going to have good outings."
Matsuzaka (7-3) earned the win, allowing an earned run on two hits and two walks while striking out six. Over his last six outings, Matsuzaka is 3-1 with a 2.95 ERA.
Despite his efficiency, Matsuzaka was pulled after using 89 pitches to complete 6 2/3 innings on Monday. Granted, he gave up a walk and two-out double before exiting in the seventh, but the right-hander said he wanted a shot to finish out the inning.
"This is the type of pitching that I really want to continue to do as the season goes on," Matsuzaka said through an interpreter. "I've got guys behind me that are all very capable -- that we can trust with the ball. That being said, even in those situations with such a small run differential, I want to become the guy that they can trust to keep me in the game."
For the second straight start, Matsuzaka had supreme command of his repertoire. He also did a great job of getting ahead in the count, as he issued first-pitch strikes to 19 of the 24 batters he faced en route to recording four 1-2-3 frames.
"He looked, to me tonight, real sharp right from the beginning," manager Terry Francona said. "I think that was obvious. ... That was real crisp. There was a lot of power to those pitches."
Matsuzaka's lone mistake came in the third inning, when he let an offspeed pitch get too much of the plate and Rajai Davis sent it over the out-of-town scoreboard in left.
But the Red Sox picked up Matsuzaka in the following frame, as Eric Patterson hit a leadoff triple to right-center and scored on David Ortiz's sacrifice fly. Adrian Beltre, who nearly signed a two-year deal with the A's in the offseason, belted a solo shot to left-center to bring the contest to its final margin.
"That was a good pitch he left over the plate, and I was able to put a good swing on it," Beltre said.
The two-run outburst was all the Red Sox needed against Ben Sheets, who allowed two earned runs on seven hits and two walks over 6 2/3 innings.
"I don't even know what that was," Sheets said of the pitch Beltre sent deep. "I've thrown that pitch 1,000 times this year and gotten outs. ... That pitch didn't do nothing except fly out of the park."
Beltre finished 3-for-4 to lead the Red Sox offensively, but appeared to favor his left hamstring after hitting his eighth-inning single.
"We all know Adrian's hamstring is killing him," Francona said. "But if he hits balls that far, it's not a real big issue."
Daniel Bard relieved Matsuzaka with runners on second and third and two outs in the seventh, but he diffused the rally by getting Gabe Gross to pop out to third base. Bard bridged the gap to Jonathan Papelbon, as he finished 1 1/3 innings of scoreless relief to lower his ERA to 1.80.
Over his past 12 outings -- a span of 12 1/3 innings -- Bard has held opponents scoreless and struck out 11 while allowing five hits and two walks.
"He's one of the premier relievers in the game," Francona said.
Papelbon then executed a perfect ninth to seal his 21st save of the season. The closer has strung together a scoreless streak of 7 1/3 innings over his past seven outings.
"He's been doing this for a while now," Francona said. "You hand him the ball and you know he's ready pitch."
With the win, Boston moved to six games back of the idle Yankees for first place in the American League East, while staying 3 1/2 back of Tampa Bay, which beat Baltimore, 8-1, on Monday.