"He had a terrific run with us," Valentine said of Middlebrooks. "He's a terrific player. I couldn't be happier or more proud of everything he did developing into the player that he is right now and contributing to our team. It's a shame."
Middlebrooks left Friday night's 3-2 win against the Indians in the ninth inning after being plunked by a 96-mph fastball from Cleveland pitcher Esmil Rogers. He was in the team clubhouse on Saturday afternoon wearing a brace on his wrist, but declined comment, saying he wanted to wait until he had more information from the medical staff.
Middlebrooks was hitting .288 with 15 home runs and 54 RBIs in 75 games this season.
"It's tough," said Red Sox second baseman Dustin Pedroia. "It seems like it's been one thing after another this whole year. Since Will's been up, he's been great. He can change the game with one swing, and he's been playing great third base. He's starting to really learn the game at this level, and you could see the game was slowing down for him. It's tough, but guys are going to have to step up in his absence and play better."
Middlebrooks isn't the first player Valentine has lost because of an injury to his hand or wrist. While managing in Japan, Valentine twice lost his best player -- Toshiaki Imae -- to a similar injury.
"We protect our elbow, and hardly ever do you see people losing a season because they get hit in the elbow, even before the elbow guards," Valentine said. "But three, four, five times a year you see people getting hit in the little parts of your hand. Eventually, they'll be a protective apparatus for those small parts."
Valentine said he isn't sure what his long-term plan at third base will be, but Valencia figures to be a primary option. The Red Sox acquired Valencia from the Twins last Sunday. The 27-year-old hit just .198 with two homers and 17 RBIs in 34 games for Minnesota this season. He batted .246 with 15 homers and 72 RBIs in 2011.
Valentine hopes Valencia flourishes in a new environment.
"It could be exactly what he needs, and exactly what we need," Valentine said. "That's why he's with us. I don't believe in coincidence."
Pedro Ciriaco was in the lineup at third base for Saturday night's game, and Valentine said he could also be an option there as well in the future. Ciriaco came up as a second baseman.
"He's been working out there a lot," Valentine said. "It wasn't a pretty look the two games in Spring Training. [Third-base coach] Jerry [Royster] feels confident that he's worked him out there enough that he can handle it."
Regardless of the replacement, losing Middlebrooks will undoubtedly hurt the Red Sox over the last seven weeks of the season. They are already without designated hitter David Ortiz, who is recovering from an Achilles injury.
"I see no silver lining with him not being in uniform," Valentine said. "I usually try to say, 'Well, maybe he needed the rest.' Or, 'It's good for one reason or another.' But I don't have that statement to make."