ARLINGTON -- In another strange but true twist in the Red Sox's season, the sauna-like conditions Sunday afternoon in Texas offered up the latest reason to believe in the revival of Daisuke Matsuzaka.

Matsuzaka worked quicker than he has all season, trying to get his teammates out of the 100-plus degree heat -- it was actually 99 degrees when the game started at 3:06 p.m. ET and 103 degrees when Dice-K departed with two outs in the seventh inning.

Matsuzaka was as sharp as he's been all season, and while the Red Sox lost 7-3 to American League West-leading Texas before 30,252 sweltering fans at Rangers Ballpark, there is reason to believe the Boston starting rotation is starting to round into pennant-race form.

Matsuzaka, who lost for the first time in eight starts, had the Red Sox in Sunday's game, trailing 1-0 into the bottom of the seventh. He ended up with a line of four runs allowed in 6 2/3 innings. Dice-K had eight strikeouts and didn't issue any walks for only the fourth time in 18 starts this season.

"Last year, things got a little bit haywire," manager Terry Francona said. "People forget he's a pretty good pitcher."

The last time Matsuzaka pitched in anything close to Sunday's conditions was when he was in high school in Japan. But that paled in comparison to Sunday, saying the Texas heat was the worst he's ever pitched in. He made a concerted effort to work quicker because of the hot weather, and that seemed to make him sharper, especially with his slider.

And in other positive aside, Matsuzaka said it was new Red Sox catcher Jarrod Saltalamacchia who helped him go more to his slider, even though it was the first time they worked together.

"At the beginning of the game, my fastball and my cutter weren't working at all -- they were probably at their worst all season -- but I noticed that my slider had a good break and Jarrod noticed that, too," Matsuzaka said. "He called the game well."

Matsuzaka had been undefeated in his last seven starts dating back to a 9-4 loss to the Rays on June 30. He was 3-0 with a 3.53 ERA in the meantime, getting stronger and pitching deeper into each game.

Matsuzaka didn't slow down Sunday, even in defeat. He went through his normal pregame routine, throwing in the outfield before the game, even though it was already in the blistering 90s.

Matsuzaka and the Red Sox fell behind, 1-0, in the bottom of the second as the Rangers' manufactured a rally. With runners at first and second and no outs, Taylor Teagarden put down a perfect sacrifice bunt to move the runners into scoring position. Andres Blanco followed with a deep fly ball to center field for a sacrifice fly, scoring Jorge Cantu.

Meanwhile, the Red Sox couldn't solve Rangers left-hander C.J. Wilson, who handled the oven that is Rangers Ballpark even better than Dice-K. The Red Sox stacked their lineup with right-handed hitters, but Wilson cruised through 7 2/3 innings, allowing four hits and a run.

"It's all in the preparation," Wilson said. "The heat is all about getting out there in it, doing you're running. That's what I do. That's just the way it is. What can I say, it felt like 81? It felt like 102. But it's every single day. It's not that bad. It's been that way for six-to-eight weeks. It's not like it was 60 for my last five starts and all of sudden it was hot."

Matsuzaka finally succumbed to Texas and the heat in the top of the seventh. Mitch Moreland led off with a single, and again the Rangers moved the runner over to third with a sacrifice bunt and a groundout. Julio Borbon then beat out a drag bunt for a 2-0 lead.

Matsuzaka's line looked a lot worse after Manny Delcarmen came in with two inherited runners and allowed a three-run home run to Michael Young for a 5-0 deficit.

The Red Sox did rally for three runs on three consecutive hits in the top of the eighth. Eric Patterson had a two-out single and scored on Marco Scutaro's double to left-center field. Darnell McDonald followed with his seventh home run of the season, a two-run shot to right field off Rangers reliever Pedro Strop.

Any thoughts of a comeback were squashed in the bottom half of the frame, as the Rangers tacked on two insurance runs.

Boston finished with a 5-5 record on a road trip that pitted it against division-leaders New York and Texas, and baseball's leading home-run hitting team, Toronto. Second baseman Bill Hill said after the game it's not a trip to be satisfied with, but that the Red Sox are still within striking distance. They trail the Yankees by six games in the AL East with 43 games to go and the Rays by five games in the AL Wild Card race.

If the Red Sox are going to make a run, the rotation of Jon Lester, Josh Beckett, Clay Buchholz, John Lackey and Matsazaka will be the reason.

"If everyone's able to pitch up their ability, we have the best rotation not only in the AL but in all the Major Leagues," Matsuzaka said.