Beavan said his elbow felt fine, but he wasn't getting the results he expected from what he thought were some quality pitches.
"I felt great out there," Beavan said. "It's just frustrating when you know you're making pitches and nothing really is going your way. You just have to keep going out there and going after guys."
Beavan walked just four batters in his first six starts this season and 19 over his first 21 Major League outings. But he issued two walks and hit a batter on Tuesday, which combined with five hits -- including a David Ortiz home run -- added up to a short day. The big right-hander is now 1-4 with a 4.58 ERA.
"He had good velocity and I thought his stuff was pretty good," said manager Eric Wedge. "But that's what they do. They're a veteran ballclub. They're not going to fish, they foul a lot of balls off and they're going to make you work for it. He didn't give in, he kept us in the ballgame, but he was in the mid-90s after four innings and that was enough for him today."
Beckett, meanwhile, threw seven shutout innings with just four hits, two walks and nine strikeouts as the Red Sox won their fifth straight to improve to 17-19.
Wedge felt his hitters had a better approach than the day's four hits showed, with numerous well-hit balls that didn't fall, including a Justin Smoak drive over the right-field pole in the second that was ruled foul and upheld after video review.
"From my view, which was right down the line, it went right over the pole, but it is what it is, I guess," said Smoak, who went 0-for-4 despite a couple well-struck balls. "They looked at it and they don't have good camera angles here, being an old stadium. The angle they had didn't show anything. So they called it a foul ball and it's a foul ball."
Wedge said balls hit right over the short foul pole at Fenway Park are "one of the toughest calls in the league." Wedge said he didn't know if the ball was fair or foul, but it definitely changed the complexion of the game.
"It does make a difference, if you can jump out to a lead and work from there," he said.
Instead, Beckett was able to cruise with a 3-0 lead and took advantage by getting a lineup filled with young left-handed hitters to strike out nine times and play to his strengths.
"They're aggressive hitters that like to pull the ball," said Red Sox catcher Jarrod Saltalamacchia. "So you try and work sinkers down and away, you tease them a little bit and give them their inside pitch, but you've got to be well located off the plate so they get their pitch and still stay with it, but you get them out away."
Beckett didn't give up a hit until Dustin Ackley reached on an infield roller leading off the fourth, extending his hitting streak to 11 games. Ichiro Suzuki followed with a one-out single to center. But hitting with runners in scoring position -- an ongoing problem -- reared its head again, as Jesus Montero and Kyle Seager left those two stranded.
The Mariners were 0-for-3 with runners in scoring position and are now 6-for-72 (.083) over their last 11 road games.
Seattle has lost 10 of those 11 road outings and now carries a 16-22 record to Cleveland, the third team on the current 10-day, four-city trek.
The Mariners have gone 10 straight games without an error, one shy of the club-record 11 set Aug. 9-21, 1993. But while they weren't charged with any errors Tuesday, they didn't play well defensively.
Shortstop Munenori Kawasaki pulled his foot off the bag early and missed on a double-play relay attempt in the fifth inning. Smoak threw wide of second when Charlie Furbush had a runner picked off later in the same frame and then let a foul pop drop behind him in the seventh when he thought Ackley had called him off.
Boston's final run in the eighth came on a double down the line by Mike Aviles when left fielder Mike Carp pulled back at the last second with the corner wall looming.
"We cost ourselves a couple runs with the defense today, no doubt," said Wedge. "No errors, but if we make a couple plays there, it saves us a couple runs -- and in that type of ballgame, that's a considerable difference."