With Jimenez set to make his Indians debut Friday night at Texas, Masterson struck out nine in six innings against his old team, leading Cleveland to a 7-3 win over the Boston Red Sox that stopped the Indians' two-game losing streak
The win also kept the Indians from falling below .500 for the first time since the third game of the season.
Another loss would have put more on Jimenez's shoulders Friday night.
"I'm sure he has a lot of other things on his mind as he's going to go out there, being a part of a new team, but hopefully that may ease a little bit for him," Masterson said after helping the Indians split the four-game series and win only their fourth in 15 games. "I know he's going to go out and pitch his game and I think we'll like what we're going to see tomorrow."
Jimenez, acquired in trade with the Colorado Rockies, has the ability to be a stopper -- but manager Manny Acta says the team now has two starters who can be counted on.
"Right now, our main guy has been Justin Masterson," the manager said. "He's a guy who from now on, and for a while now, we have tried to keep him on the five days routine because he's the guy that we want to see out there every five days. It's good that Ubaldo doesn't have to feel like he's a guy who's going to stop it every time."
Carlos Santana, who struck out four times Wednesday night, snapped a 3-3 tie with a two-run homer in the sixth inning and drove in three runs with three hits, while Travis Hafner and Kosuke Fukudome also collected three hits.
The loss dropped the Red Sox into a tie with the New York Yankees for first place in the AL East. The Yankees, winners of seven straight, come to Fenway for a three-game series starting Friday night. Boston, 8-1 against New York this season, has been in first place since July 7.
Masterson (9-7), traded by Boston to Cleveland in the Victor Martinez deal in 2009, raised his Fenway record to 10-2. He is 15-33 everywhere else. He is also 3-0 against the Red Sox.
"He's good ... we see his best," said Red Sox manager Terry Francona. "I am sure that he enjoys pitching against us. He's impressive."
Masterson tied a major league record with four strikeouts in the second inning, thanks to a wild pitch on a third strike. He is the sixth Indians pitcher -- the first since Chuck Finley in 2000 -- to fan four in an inning.
Erik Bedard, making his Red Sox debut after being acquired from the Seattle Mariners, gave up three runs and seven hits in five innings. In his second start since coming off the disabled list, he was on a pitch count and came out after 70 with the score tied 3-all.
Hafner greeted reliever Franklin Morales (0-1) with a long double and, on the next pitch, Santana, already 2-for-2 with an RBI, hit his 16th homer to dead center field. It was only his second home run of the season right-handed.
Hafner's RBI double off Andrew Miller in the seventh and Fukudome's RBI double closed the scoring in the ninth.
The Red Sox took a 2-0 lead in the first on an RBI double by Adrian Gonzalez and run-scoring single by David Ortiz. Gonzalez extended his season-best hitting streak to 14 games with his major league-leading 91st RBI.
The Indians tied the game on Matt LaPorta's infield hit (Bedard failed to cover first) and an RBI grounder by Austin Kearns in the second, and Santana's RBI single made it 3-2 in the third. Reddick tied the game again with his fifth homer of the year.
The game drew 38,477 a post-World War II record at Fenway. ... Jimenez makes his Indians debut when he faces 10-game winner Derek Holland, who shut the Indians out June 4, in the opener of Clevelands three-game series in Texas on Friday night. ... Jon Lester, 8-1 lifetime against the Yankees and 2-0 this season, faces New York's Bartolo Colon, 0-2 against Boston this year, on Friday night. ... Indians left fielder Michael Brantley missed his second straight game with a sore right wrist. He will take batting practice Friday. Meanwhile, right fielder Shin-Soo Choo, on the disabled list with a broken left thumb, is hitting and appears to be ahead of the projected return of the last week of August or first week of September. ... Indians outfielder Travis Buck accepted his assignment to Triple-A Columbus. ... Cleveland right-hander Carlos Carrasco, who started Wednesday night, dropped his appeal and began serving a six-game suspension for throwing high to the Kansas City Royals' Billy Butler. ... Indians second baseman Jason Kipnis saw his home run streak end at four straight games. He is the first player in major league history to homer in four straight within two weeks of the start of his career. Graig Nettles, then of the Minnesota Twins, was the last player to homer in four straight in the first 10 games of his career, doing it in 1968. Kipnis is the first Indians second baseman ever to accomplish the feat. ... Miller, in his first Red Sox relief outing, threw 71 pitches in 2 2/3 innings.