HOUSTON – The Boston Red Sox spent the first six games of this trip struggling on offense.

They have busted out since coming to Houston.

Darnell McDonald hit a three-run homer Saturday night, pinch-hitter Yamaico Navarro went deep for the first time, and the Red Sox beat the Houston Astros, 10-4.

Dustin Pedroia, Adrian Gonzalez and Kevin Youkilis each had three hits and drove in a run for the Red Sox, who have won three straight.

Boston has 17 runs in its last two games after managing just 15 in the previous six.

Manager Terry Francona said figuring out why a team goes through spans where it struggles to score is difficult.

“That’s why when you are not scoring, you don’t have to like it but you don’t need to panic, you don’t need to change things up, you just keep running them out there because they’re good hitters,” he said. “You’re going to go through periods where it just doesn’t work.”

Navarro, a former Portland Sea Dog, hit a solo shot in the seventh for his first major league homer. McDonald’s drive in the eighth landed on the train tracks atop the wall in left field and stretched the lead to 9-3.

McDonald was in a 3-for-34 slump before the homer.

“I know things are going to turn around for me,” he said. “I’m working hard. I’ve been feeling good at the plate, I just haven’t been getting results. So it feels good to get rewarded with the home run, but the main thing is just getting something positive going.”

One night after rallying for six runs in the seventh inning of a 7-5 victory against the Astros, the Red Sox got off to a fast start against J.A. Happ.

Gonzalez had an RBI single and David Ortiz, playing first base in the NL park, walked with the bases loaded to force in another in the first inning. Pedroia added an RBI double in the fifth.

That was more than enough for Andrew Miller (2-0), who yielded two runs and seven hits in six innings for Boston.

Happ (3-10) left with two outs in the seventh, and was charged with five runs and seven hits. He has dropped a career-worst six consecutive decision and Houston has lost his last nine.

“They’re tough,” Happ said. “They’re a good ballclub. They pitched better, hit better and played better defense than we did. That’s why they won.”

Hunter Pence homered and drove in two runs for the last-place Astros, who have lost 13 of 17. Michael Bourn tied a career high with four hits.

“We battled them, we hit the ball hard sometimes,” Bourn said. “We could have gotten a break that could have started something. Other than that, we’ve got to find a way to just learn. That’s it.”

Navarro, who was called up from Triple-A Pawtucket before Thursday’s game, hit his homer to the first row in left field with one out in the seventh. It was the second pinch-hit homer by a Red Sox player this season.

Navarro had trouble getting onto the field before his homer.

“I couldn’t find my helmet,” he said in Spanish. “(Francona) was like, ‘Let’s go, you’re up next.’ I just took somebody’s.”

Boston reliever Alfredo Aceves gave up consecutive singles to pinch-hitter Jeff Keppinger and Bourn with two outs in the bottom half before walking pinch-hitter Matt Downs. He was replaced by Daniel Bard, who walked in a run before retiring Carlos Lee to limit the damage.

Boston started the eighth with three consecutive singles and Jarrod Saltalamacchia’s sacrifice fly made it 6-3.

Bourn extended his hitting streak to 11 games with a leadoff triple in the first. Angel Sanchez drove him in with a single.