Tazawa took his second defeat of the season in the Red Sox's 4-3 loss to the Rangers on Sunday at Rangers Ballpark in Arlington, allowing 10 hits, three walks and four earned runs over five-plus innings. His 97 pitches were split between 54 stikes and 43 balls.
The Red Sox now trail the Rangers by a half-game in the Wild Card race and finished 2-7 against Texas this season.
"[The Rangers are] pitching really well," second baseman Dustin Pedroia said. "They located all their pitches. I saw a lot of pitches last year to drive. We lost a one-run game to a good team. It happens.
"We had chances. They made good pitches."
The loss continues the Red Sox's recent difficulties. They are 12-17 since the All-Star break, going 5-13 on the road since then and have lost five of six series.
Boston has lost three consecutive road series and is 11-20 against the AL West and 1-8-1 in series against the division this season.
"I was aware of the situation we have, heading into the playoffs," Tazawa said through a translator. "I wanted to contribute. Overall, it wasn't what I wanted. It was not the Rangers. It was my pitches."
Especially his fastball.
"I didn't think he had his best fastball," manager Terry Francona said. "He didn't strike anyone out. That says he doesn't have the best life on his fastball. He was always around the plate."
Tazawa pitched into a couple of jams at the start of the game, and a little bit of fortune helped bail him out.
The Rangers had runners on first and third with one out in the first inning when Marlon Byrd lined a ball right at Pedroia. He threw to first to double off David Murphy, who thought the ball was going to get through the middle.
The Rangers had Taylor Teagarden on first an inning later, and Elvis Andrus laced a ball to deep center field that bounced over the fence for a ground-rule double. Teagarden would've scored on the play, but he was held at third.
Tazawa induced a fly out to end the Rangers' two-on, two-out threat.
"Overall, my pitches were a little too high," Tazawa said. "Especially my fastball, but some pitches were a little too high. I wanted more control of my breaking ball."
David Ortiz jump-started the game's scoring, belting a solo home run in the second inning. Ortiz has hit safely in eight of nine games against the Rangers this season, going 11-for-31 (.355) with three home runs and six RBIs.
The Rangers tied the score at 1 when Ian Kinsler hit a home run of his own a half-inning later. They would add back-to-back RBI hits in the third to push the score to 3-1.
The Red Sox brought the score to within one, 3-2, on a sacrifice fly by Brian Anderson that scored Ortiz in the fourth.
Teagarden led off the sixth with a home run to push the Rangers' lead to 4-2, but Pedroia followed that with a solo home run of his own a half inning later.
It was Pedroia's 10th home run of the season. He became the first Red Sox second baseman with back-to-back double-digit homer seasons since Mike Andrews in 1969-70 and the third to do it since Bobby Doerr achieved it every season from 1939-1951.
The Red Sox had a huge opportunity in the eighth when they put runners on first and second with one out, but Rangers reliever C.J. Wilson got Anderson and shortstop Alex Gonzalez to strike out looking to end the threat.
"We couldn't gather a few hits in a row, but that's how it goes sometimes," shortstop Nick Green said. "One big hit here and there, and we could've won the game."
The Red Sox had at least one baserunner in every inning except the ninth and stranded nine runners overall.
"We just need to score some runs," Green said. "We got to score some runs when we put them out there. Any time you get runners out there and don't put them across, it's bad."
Boston's offensive struggles weren't limited to Sunday. Not counting the six-run outburst against Rangers closer Frank Francisco in Friday's 8-4 victory, the Red Sox scored only seven runs the entire series.
"[It's] one of those things where good pitching beats good hitting," Green said. "Their starting pitching has been good, and their seventh through ninth is good, too. Once their starting pitching makes it to the seventh, it's difficult."
The Red Sox's offensive malaise should be helped by the addition of Kevin Youkilis, who returns Tuesday from a five-game suspension that began on Wednesday. Boston went 2-3 while he was out of the lineup.
"[Youkilis is] one of the best players in the game," Pedroia said. "We tried to hold the fort down while he was gone."
The Red Sox couldn't quite do so, but adding Youkilis may help them retake the lead in the Wild Card standings.
Daniel Paulling is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.