BOSTON—On June 22, Adrian Gonzalez was batting .256, 103 percentage points lower than the .359 he was batting on the same date last year, his first with the Red Sox.

Gonzalez was batting an American League-leading .400 (60 for 157) in 38 games since then entering play Tuesday night, raising his average 51 percentage points to .307, the highest it has been since mid-April. He has hit safely in 11 of his last 12 games, a stretch in which he is batting .463 (19 for 41) with an on-base average of .522 and a slugging percentage of .683. He has 2 home runs and has driven in 11 runs in that span.

Only two Sox players are batting .300 since Gonzalez began his six-week long tear: David Ortiz (.359) and Pedro Ciriaco (.338). Gonzalez’s 33 RBIs are 11 more than any Sox player in that span, while his 6 home runs are just one fewer than the 7 hit by Cody Ross and Jarrod Saltalamacchia. Gonzalez’s OPS in that span is an even 1.000, with an on-base average of .427 and slugging percentage of .573.

Last season, when he competed in the home run derby, Gonzalez began the second half slowly, batting .083 (2 for 24) in his first five games after the break before embarking on a 14-game hitting streak. This season, Gonzalez had two or more hits in each of his first five games after the break, and has had multi-hit games in 13 of the 22 games in which he has played since then.

For the better part of two seasons, Gonzalez had cut down on his swing out of necessity, because of a bum right shoulder that ultimately required surgery after the 2010 season.

He came to spring training this season feeling great, convinced that he would be able to turn on the ball with the authority he had displayed in 2008 and ’09, when he hit a combined 76 home runs despite playing in cavernous Petco Park in San Diego.

“I was thinking how great it would be to follow through again with my bat extended up here,’’ Gonzalez said recently, demonstrating a swing in which his bat hand wound up elevated well above his head, his torso fully torqued.

While hurt, Gonzalez had not exactly become a slap hitter, but now he was ready to unleash the full force of a swing that even in diminished form had produced 17 home runs in the first half of the 2011 season, his first with the Red Sox, before tapering off to 10.

Then the oddest thing happened: The home runs did not come. Two in 98 plate appearances in April. Two in 127 plate appearances in May. Two in 114 plate appearances in June.

And with the absence in power came something equally as puzzling: a drop in average, to the .256 on June 22. But now the power is returning, too, with 5 home runs since the midseason break, one fewer than he hit in the season’s first half.

“People say, where has my power gone? It hasn’t gone anywhere,’’ Gonzalez said. “My mechanics were out of whack. I was trying to force something that wasn’t happening. I got to the point where I said, ‘How long am I going to be this guy trying to get to be [power] guy and I’m not producing? So I just tried to hit singles.

“Isn’t a 2 for 4 with two singles and an RBI better than an 0 for 4, trying to hit home runs?’’

Gonzalez said he didn’t feel pressure to hit home runs.

“I don’t feel pressure,’’ he said. “I play for the guys in here. I don’t care about that stuff. All I care about is trying my hardest every day and keeping my head high. I wasn’t worried about people writing that I’m not producing. I’m trying my hardest. What else can I do?

“I was trying to hit home runs. I was trying to drive the ball because I was healthy. For years I was doing it with a shortened stroke. Now I was healthy, my shoulder was healthy, I was trying to force something.

“Then I changed my approach. I had tried everything and decided to just try and hit singles I don’t care if I hit five more home runs the rest of the season.’’