Jimenez struck out a season-high 10 for his first win in more than a month and the Indians beat Boston 5-3 on Thursday night, handing the Red Sox their seventh loss in nine games.
The performance came too late, however, to save the job of pitching coach Scott Radinsky, who had worked with the talented but erratic right-hander all season. Radinsky was fired by the Indians earlier in the day.
"A great job by Ubaldo," manager Manny Acta said. "That was probably his best command of the fastball. He was just dotting it on both sides."
Jimenez (9-11) allowed three runs over six innings as Cleveland won its second straight after losing 11 in a row. He had been 0-4 with an 8.41 ERA in five starts since beating Tampa Bay on July 7.
"This was the best for me," Jimenez said. "I threw the breaking ball for strikes as well as the fastball."
Chris Perez earned his 30th save in 34 chances. He pitched a perfect ninth after blowing saves Sunday and Tuesday, allowing eight runs over 1 1/3 innings in those two appearances.
It was Perez's first clean-shaven outing of the season. The All-Star closer cut off his scraggly beard before Wednesday's game, when Cleveland beat Minnesota to end its losing streak.
"It looked like we forgot how to play ball," Perez said of the embarrassing slide. "We want to win more than anybody, but everybody went into a slump together.
"We're 2-0 since I shaved, though. Baseball is a game of adjustments. I had to do something."
Asked to assess how Perez looked, Acta quipped: "Very white. He needs a suntan now."
Cleveland improved to 24-13 in series openers, second to the New York Yankees' 24-12.
It wasn't how the Red Sox wanted to open a 10-game trip that includes three-game series against AL East rivals Baltimore and New York.
Boston ran itself into a double play in the seventh. With one out and Pedro Ciriaco on second, Carl Crawford grounded a pitch from reliever Tony Sipp to shortstop. Asdrubal Cabrera fielded it and threw to third, putting Ciriaco in a rundown. Cabrera took third baseman Brent Lillibridge's return throw, tagged Ciriaco, then whirled and threw to second to nail Crawford, too.
"Pedro was a little overaggressive there," Boston manager Bobby Valentine said. "The ball was hit real hard. His first move was to score."
Jimenez leads the AL with 77 walks, but the only free pass he issued Thursday was to the first batter of the game, Jacoby Ellsbury.
"He was throwing the ball on the outside corner or wherever the heck it was," Valentine said. "He was getting every pitch called a strike. That's what I saw."
Jimenez credited Radinsky with patiently and persistently working to smooth out his delivery.
"I'm going to be always grateful for what he did for me," Jimenez said. "He did all he could to help. He's going to be a good pitching coach (somewhere) for a long time."
Donald homered on the third pitch he saw from Doubront after being recalled from Triple-A Columbus when designated hitter Travis Hafner went on the disabled list with lower back inflammation. Donald was a late lineup replacement for second baseman Jason Kipnis, scratched with a sore neck.
Adrian Gonzalez hit a two-run homer in the Boston fourth. Half of Gonzalez's six career hits off Jimenez have been homers. He was 5 for 28 against the right-hander before pulling a 1-1 pitch to right.
Dustin Pedroia's RBI single made it 3-1 in the fifth. Ellsbury singled and got in scoring position by stealing second -- his third steal of the game. Opponents are 30 for 34 stealing against Jimenez's deliberate delivery.
The Indians went back in front in the bottom half. They tied it at 3 on an RBI double by Cabrera and Carlos Santana's run-scoring single. Andrew Miller came on with the bases loaded and yielded a go-ahead sacrifice fly to Michael Brantley.
Donald's RBI grounder in the eighth made it 5-3.
Indians RHP Joe Smith termed Radinsky's firing "a shock, but the business side of baseball." ... Boston DH David Ortiz, out since July 18 with a sore heel, is slated to run the bases Friday. He could be activated Sunday. ... Valentine said RHP Josh Beckett felt no discomfort in his back or shoulder Wednesday when he allowed eight runs in five innings to Texas in his first start since July 31. ... Indians RHP Roberto Hernandez is scheduled to start Friday for Columbus. His three-week suspension for playing under the false name of Fausto Carmona ends Saturday. ... Red Sox reliever Andrew Bailey (thumb surgery) struck out two in a scoreless inning during a rehab outing for Triple-A Pawtucket. Bailey, acquired from Oakland in the offseason to be Boston's closer, has been out since spring training.