BOSTON (AP) -The Red Sox will quickly learn if they are in a hitting groove or if all the runs they racked up against the Rangers was thanks to Texas' pitiful pitching.

David Ortiz hit a three-run homer to highlight a nine-run second, and the Red Sox used their second big inning in three games against the Rangers to help Daisuke Matsuzaka win 10-0 on Thursday night for a three-game sweep.

''I don't know,'' Boston's Dustin Pedroia said of what led to the three-game outburst. ''We'll find out the next couple of games.''

The Red Sox go from facing the team with the worst ERA to playing the team with the best, Toronto, which had a league-high 3.64 ERA entering Thursday.

Matsuzaka allowed six hits in seven innings for the Red Sox , who scored 37 runs in the series and won their fourth straight to remain three games behind AL East-leading Tampa Bay. The Rays beat Oakland 7-6 in 12 innings.

Boston scored its most runs in a three-game set since getting 45 against the Florida Marlins from June 27-29, 2003.

Boston topped its nine-run inning with a 10-run frame in the first inning Tuesday - a 19-17 victory. Ortiz had a pair of three-run homers in that inning and has driven in 20 runs against the Rangers in seven games this season.

Unlike Tuesday when the Red Sox fell behind 16-14 after leading by 10 twice, they relied on Matsuzaka's strong outing to keep the Rangers from mounting a comeback.

''When he settles in, when there are runners on base he executes pitches,'' Boston manager Terry Francona said. ''He gets comfortable, gets in his delivery and gets in the flow of the game and really pitches well.''

Matsuzaka (14-2) walked five and struck out five. Manny Delcarmen and Mike Timlin each worked a perfect inning to complete the shutout.

Matsuzaka wasn't impressed by his outing.

''We got all those runs near the beginning of the game, so I should have been able to go out there and get outs at a better pace, but I wasn't able to,'' Matsuzaka said through a translator. ''I felt like I was struggling to get into a good groove all game.''

Not as bad as Texas' pitchers.

The high scoring is nothing new for the Rangers' staff, which entered the game with a major league-worst 5.41 ERA. It was their seventh loss in eight games, and they've allowed 62 runs in the last six.

''Pitching, pitching, pitching,'' Rangers manager Ron Washington said was the word that described a 1-5 road trip. ''Of course you're embarrassed. We're all embarrassed because we feel we're better than that.''

Texas starter Tommy Hunter (0-2), making his third career start, was charged with all nine runs in 1 2-3 innings Thursday.

''You think that,'' Hunter said, when asked if he felt he needed to be almost perfect after watching Boston's hitters the previous two nights. ''Our bullpen definitely didn't need to be in there for nine innings. I wish I would have done better.''

Matsuzaka loaded the bases on two walks and a single in the second, but fanned Ramon Vazquez to end the threat.

The Red Sox loaded the bases in the bottom of the inning on a singles by Kevin Youkilis and Jed Lowrie and a walk to Jason Varitek . Coco Crisp 's RBI single pushed Boston ahead 1-0.

Alex Cora was hit by a pitch and J.D. Drew's fielder's choice grounder made it 3-0. Pedroia followed with an RBI double before Ortiz homered into the first row of the right-field seats, making it 7-0. Jason Bay 's RBI single and Lowrie's run-scoring double completed the outburst.

Notes: Rangers OF Josh Hamilton left the team early Thursday morning and flew back to Texas to be with his wife, Katie, who gave birth to the couple's third daughter, Michaela Grace. ... The Red Sox are a season-best 20 games over .500. ... Boston won all seven games at home against Texas this season. ... The Atlantic Coast Conference baseball tournament, originally scheduled for Fenway in 2009, will be moved to another venue next year due to a scheduling error. The league and Fenway Sports Group, owned by the Red Sox , said it will be in Fenway in 2010. ... RHP Paul Byrd , acquired from Cleveland Tuesday for either cash or a player to be named, is scheduled to make his Red Sox debut against Toronto on Friday. ... Rangers RHP Kevin Millwood , on the DL since July 24 with a strained right groin, is expected to be activated and start against Tampa Bay Friday night in Arlington, Texas. ... Pedroia has hit safely in 40 of 44 games. ... Hunter started in place of Vincente Padilla, scratched Wednesday with an inflamed muscle in his neck. Padilla is expected to start Sunday.