Matsuzaka pitched eight solid innings and Beltre hit a grand slam to lead Boston to a 6-2 victory over the Cleveland Indians on Thursday night, earning a split of the four-game series.
"Every game from here on is a must win," Matsuzaka said, "so I think the most important things about today is we got a 'W.'"
Going into their game on July 4, the Red Sox were a half-game out of first place in the AL East. Now, after a rash of injuries, they trail the first-place New York Yankees by six games for the division lead and Tampa Bay by 5 1/2 in the wild-card race.
Matsuzaka (8-3) allowed Shin-Soo Choo's 14th homer of the season in the first but gave up just four more hits and never faced more than four batters in any inning. He is 5-1 in his last 10 starts and has allowed three earned runs or less in 10 of his last 12 outings.
"Matsuzaka had tremendous control and he was tough," Indians manager Manny Acta said. "We aren't claiming to be a hitting machine type of club, but he had a good arsenal."
He struck out six, walked two and allowed five hits. After Jayson Nix led off the seventh with a single, Matsuzaka retired the last six batters he faced, finishing by getting Choo on a groundout.
"I knew that if I let anybody on base that would be the night for me, so I needed to get those [last] three outs," Matsuzaka said.
Beltre is batting a team-high .336 with 20 homers and a club-leading 75 RBIs. He connected for his grand slam in the fourth off Josh Tomlin (1-1), who retired Boston's first 10 batters.
"It was a fastball right in the middle," Tomlin said. "I lost the first few hitters and got out of rhythm. The fourth inning killed me and I paid when I made a mistake."
Matsuzaka "gave us a lot of pitches to hit and we just didn't," Crowe said. "He challenged us, but we just didn't take advantage."
Marco Scutaro singled with one out in the fourth for Boston. After David Ortiz flied out, Victor Martinez and J.D. Drew walked before Beltre hit a 1-0 pitch for his eighth grand slam and first since Sept. 21, 2006. It extended his hitting streak to 11 games during which he's batting .356.
"He continues to just take ferocious swings without losing sight of what he's doing," Red Sox manager Terry Francona said.
The homer capped Beltre's big series against Cleveland. He started it by driving in all of Boston's runs in a 6-5 loss Monday night and finished 6 for 15 with four runs scored, three homers and nine RBIs.
Drew drove in Boston's last two runs in the eighth with a single.
The Indians lost a chance for their first series win at Fenway Park since 2005, while the victory sent the Red Sox off on a tough 10-game road trip on a high note. They open a four-game series against the Yankees on Friday night, then play three games each at Toronto and Texas.
Boston is trying to stay in contention without some of its best hitters. The latest to be sidelined is first baseman Kevin Youkilis, who is scheduled to undergo season-ending surgery on his right thumb on Friday in Cleveland. Second baseman Dustin Pedroia missed his 34th game Thursday with a fractured left foot and still can't run without pain.
Matsuzaka was coming off one of his poorer outings of his strong season when he left last Saturday's game in the seventh with Detroit leading 4-0. But Boston rallied for a 5-4 win.
Tomlin started the game the way he pitched in his first two major league starts. He allowed one earned run in seven-plus innings and got the win in his debut, a 3-1 win over the Yankees, then got a no-decision in a 2-1 win at Toronto in which he gave up one earned run in 5 1/3 innings.
Tomlin settled down after Beltre's homer, giving up two more hits before leaving after the seventh.
"He's human," Acta said. "Here and there he will lose his command, but after the grand slam he still went about his business and kept his composure."
Ortiz's 13-game hitting streak ended when he went 0 for 3. ... Choo's homer extended Cleveland's streak to 58 games with an extra-base hit, the longest current stretch in the majors. ... Before the game, the Indians acquired C Juan Apodaca and IF Argenis Reyes, who have been at Boston's Triple-A team in Pawtucket, for cash. ... Matsuzaka is 4-0 with a 0.93 ERA in his last four starts against Cleveland.