BOSTON (AP) The way Justin Masterson was pitching, he didn't need much help. The Orioles gave it to him, anyway.
On a rainy, chilly Patriots' Day holiday, Baltimore made three errors that led to five unearned runs, Wei-Yin Chen struggled with his control and the Boston Red Sox won 7-1 Monday in a game shortened by rain to 6 1/2 innings.
''The errors kind of gift-wrapped or built into the four-run inning, along with some bases on balls,'' Boston manager John Farrell said. ''At this level, you give extra outs, you're asking for trouble.''
The first pitch was thrown at 11:04 a.m. after Boston Marathon runners already were on the course that passes close to Fenway Park. Rain began falling steadily in the fourth inning, and the game was called after a 1-hour, 42-minute wait.
''It was the same for both teams,'' Baltimore manager Buck Showalter said. ''It was a little bit hard for anybody on the mound to throw the ball where they wanted.''
Masterson (2-0) allowed one run, three hits and three walks in five innings with six strikeouts. He didn't want to change his plan to get five innings in before the rain, to make the game official.
''We're not just laying balls in there, because that's kind of the way things snowball,'' Masterson said. ''All of a sudden now you've got the bases loaded and you're giving up a grand slam or putting people in a bad spot.''
With the score tied at 1, Boston scored four runs in the third when Chen walked four and made an error, and third baseman Manny Machado committed another error.
Chen (0-1) thought plate umpire Andy Fletcher had a small strike zone.
''When you make a pitch and can't throw it for a strike, you can't throw the next pitch down the middle,'' Chen said through a translator. ''It kind of upset me.''
Chen gave up three hits and five walks after getting the win in Baltimore's 7-6 victory at Fenway last year on Patriots' Day, which commemorates the first battles of the Revolutionary War.
Boston took a 1-0 lead in the first when Mookie Betts singled, stole second, took third on catcher Ryan Lavarnway's wild throw and scored on David Ortiz's sacrifice fly.
Baltimore tied it in the second on Travis Snider's triple and Ryan Flaherty's double.
Xander Bogaerts led off the third with a walk, took third on a single by Ryan Hanigan and scored when Chen bobbled Betts' grounder. Dustin Pedroia sacrificed, and Allen Craig loaded the bases with a walk.
Mike Napoli walked, forcing in a run, and Machado's error allowed Betts and Craig to score.
Baltimore had three errors, the first game this season in which the Orioles committed more than one. They have seven errors this year, three by pitchers.
Boston made it 7-1 in the sixth. Hanigan was hit for the second time and scored on Pedroia's double off Jason Garcia. After Ortiz was walked intentionally, Craig singled in Pedroia.
Baltimore's Adam Jones had his nine-game hitting streak snapped after going 7 for 10 in the previous two games.
Three-time Boston Marathon winner Bill Rodgers threw out the ceremonial first pitch. It reached Wade Miley, Boston's left-handed pitcher who was behind the plate, on a fly.
The Red Sox earned a split of the four-game series after winning their other three so far this season.
Orioles: Showalter thinks INF Jonathan Schoop, who went on the 15-day disabled list with a sprained right knee Saturday, could be back sooner than the six to eight weeks originally forecast. Schoop is rehabbing in Sarasota, Florida.
Red Sox: LF Hanley Ramirez left in the top of the third because of illness. He was replaced by Craig. 3B Pablo Sandoval was out of the lineup for a day of rest. Brock Holt (12 for 24 coming into the game) started in his place and went 0 for 2.
Orioles: RHP Bud Norris (0-1, 12.38 ERA) pitches Tuesday the opener of a three-game series in Toronto against LHP Mark Buehrle (2-0, 3.75). Norris won his last start, allowing three runs in five innings against the New York Yankees. In his other start this year, he gave up eight runs in three innings in a loss to Toronto.
Red Sox: Miley (0-1, 10.57) pitches the opener of a three-game series at Tampa Bay on Tuesday against RHP Chris Archer (2-1, 1.37). It begins a six-game trip. In his last start, Miley allowed seven runs in 2 1-3 innings in his Fenway debut, a 10-5 loss to Washington this season.