In his first trip to the Bay Area on Tuesday night, Matsuzaka pitched seven innings, yielded two runs and struck out eight batters.
He also gave up seven hits and two walks and he allowed a baserunner in every inning except for his last in Boston's 2-0 loss.
"I had problems with my overall command," Matsuzaka said. "When I'm having problems, I try to change the tempo and see what happens. I try to throw strikes to keep [our] offense in rhythm, but tonight I didn't do that."
Most times, allowing two earned runs over seven innings will get you the win, especially when pitching for a team with the third best offense in baseball. But on Tuesday night, the Red Sox suffered their first three-game losing streak.
"They made him work hard tonight," Red Sox manager Terry Francona said. "But after seven innings and two runs, more often than not you're patting him on the back."
The A's draw walks at the second-highest rate in Major League Baseball, walking 235 times after Tuesday's victory and are known for having patient hitters. The only team that draws more is the Red Sox, who have accepted 245 free passes.
"They are a team with great batters eyes and are very patient," Matsuzaka said of the A's. "But before I concern myself with the other team's lineup, I should assess my own pitching performance, which I wasn't very happy with today."
He threw a season-high 129 pitches, 77 of them for strikes. His previous high was 124 on May 14, when he threw a complete game in a 7-1 win over Detroit.
"Certainly with the situation I would have been expected to pitch a complete game in Japan," Matsuzaka said. "Pitch count is something I'm not too concerned about."
His record dropped to 7-4 on the year despite his ERA falling from 4.83 to 4.63.
"He's just a good pitcher," Francona said. "When he's got it going on he's pretty good. They're still a learning curve."
Matt Smith is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.