BOSTON – The Boston Red Sox loaded up on offense. They had a strong rotation. Their rebuilt bullpen looked promising.

Then they started playing. Six games, all losses.

The season many thought would end with a World Series berth began with Boston’s longest season-opening losing streak since going 0-8 in 1945. And after 12 games this year, the Red Sox were 2-10.

Then they got on a roll. After 51 games, they already were tied for first in the American League East. Coming out of the All-Star break, their 55-35 record is second in the majors behind the Philadelphia Phillies.

“It was a very difficult start. There’s no getting around that,” Manager Terry Francona said after Boston entered the break with a six-game winning streak. “We were taking some pretty good shots. We probably deserved them, but there were some things that were being written or said that I don’t think I believe.

“I think we went out and proved that we can be a good team. We’re not done yet, not even close, but we’re playing better baseball.”

Boston’s 55-29 record starting with its first win — 9-6 over the New York Yankees in the home opener — is the best in the majors since then.

The reality, though, is this: Through good and bad, the only record that matters is the one at the end of the regular season.

“We just had a nice first half after a real rough start,” General Manager Theo Epstein said, “and I’m proud of the guys, but it won’t mean anything if we don’t come out and play good baseball (in) the second half. What matters is where you finish and then what you do in October.”

Despite leading the Yankees by one game in the division and having baseball’s best offense, the Sox have some concerns.

Three of their original five starters are on the disabled list. Jon Lester and Clay Buchholz are expected to return soon from back problems, but Daisuke Matsuzaka is out for the year following Tommy John surgery on his right elbow.

Carl Crawford also should be back shortly after nearly a month on the disabled list with a hamstring injury.

Going into a three-game road series against Tampa Bay starting Friday, the Red Sox lead the majors in batting average, runs, hits, doubles, RBI, walks, on-base percentage and slugging percentage.

Adrian Gonzalez is the best hitter in baseball’s best lineup, tied for the major league lead with a .354 batting average and first with 77 RBI, 128 hits and 29 doubles. He’s thriving since moving from pitcher-friendly Petco Park in San Diego to Fenway Park.

He’s only walked 35 times in 89 games, but he doesn’t lack patience. Instead, pitchers are reluctant to pitch around him with Kevin Youkilis (.285, 63 RBI) and David Ortiz (. 304, 19 homers) following him in the batting order.

The first two batters — Jacoby Ellsbury (.316) and Dustin Pedroia (.284) — are just as potent.

One worry is the health of the pitchers: The top three starters, Lester, Buchholz and Josh Beckett (back), are ailing. In the bullpen, Bobby Jenks had two stints on the disabled list with a strained biceps and tight back and has a 6.32 ERA.

But the relief corps is deep. Setup man Daniel Bard has thrown 191/3 straight scoreless innings in his last 18 appearances, Jonathan Papelbon has 20 saves in 21 opportunities, Matt Albers hasn’t allowed a run in 14 of his last 16 outings and Dan Wheeler has held opponents scoreless in 14 of his last 17.

Still, the Red Sox are in a tough division. The Yankees have kept pace despite Derek Jeter’s recent 20-day stint on the DL.

“It’s nice to be where we are given where we started,” Epstein said. “We haven’t really proven anything yet although, hopefully, we’ve answered some questions about how we bounce back from adversity.”