Jon Lester and the Red Sox concluded their disappointing first half with a 7-3 loss to the Yankees. (AP)

Since he became a fixture in the Red Sox rotation in 2008, Jon Lester has been the most consistent starter on his staff. In each of the last four years, he’d finished with at least 15 wins with a sub-3.50 ERA, joining CC Sabathia and Roy Halladay as the only pitchers in the majors to pull off that feat four straight times. What’s more, he’d never had a half-season over the last four years in which his ERA snuck above 4.00. He has been the constant, a pitcher whose excellence almost could be taken for granted by the Red Sox as they built out the rest of their rotation.

On Sunday, Lester concluded a first half of the 2012 campaign that defied his career norms. The Yankees knocked him out of the game after just 4 1/3 innings, collecting nine hits (six singles, two doubles and a triple) and five runs (four earned). Though Lester had six strikeouts and two walks, the Yankees refused to expand the strike zone against him, and on a night where he threw strikes on just 55 percent of his pitches, the left-hander needed 101 pitches despite the fact that his night ended in fewer than five innings.

His struggles — which included a two-run yield in the first inning, continuing the Sox’ woes in the game’s inaugural frame — set the stage for a 7-3 Red Sox loss, and the team now finds itself with a .500 record (43-43) and 9 1/2 games behind the Yankees at the All-Star break. It is the first time in 15 seasons (since 1997) that the team has not been above .500 at the break, something that reflects in no small part on the fact that the Sox simply haven’t had a consistent top-of-the-rotation presence throughout the season.

Lester arrives at the break with a 5-6 record and 4.49 ERA, with the ERA ranking 77th among the 101 pitchers with enough innings to qualify for the ERA title. The Sox are 7-11 when he takes the mound. In short, one of the anticipated centerpieces of the team has not lived up the considerable standards that he’s established, a common theme on a Red Sox team that should be characterized as a disappointment through the first half of the year.

WHAT WENT WRONG FOR THE RED SOX

–Adrian Gonzalez saw his 18-game hitting streak come to an end when he was replaced after just two innings due to what the Red Sox described as illness. He struck out in his only plate appearance of the night. During the run, Gonzalez hit .377 with a .400 OBP, .481 slugging mark, .881 OPS, five doubles and one homer. He arrives at the break with a .283 average, .745 OPS and six homers, with both the OPS and home run total representing the lowest marks for a full half in his career since he became a big league regular in 2006.

– Jarrod Saltalamacchia went 0-for-4 with three strikeouts and stranded seven runners. Though he has two homers in July, those are his only hits in the month, as he’s gone 2-for-25 to drop his average to .235 with a .798 OPS.

– Daniel Nava skidded into the All-Star break with an 0-for-4 game (though he did draw a walk) and a pair of strikeouts. He went 7-for-46 (.146) with a .241 OBP in his final 12 games before the All-Star break.

– Scott Atchsion saw his tremendous first half end on a down note. Coming on in relief of Lester, he pitched two shutout innings before giving up a double to Nick Swisher and a two-run homer by Andruw Jones. The homer was the first given up by Atchison since April 17, snapping a run of 31 consecutive appearances without permitting a longball. Even so, the right-hander finishes the first half with a 1.79 ERA in 45 1/3 innings, and 12 outings of at least two innings.

WHAT WENT RIGHT FOR THE RED SOX

– David Ortiz went 1-for-4 with a double and a walk, finishing the first half with a .312 average and a 1.013 OPS, the latter of which represented a career first-half high.

– Mark Melancon tossed 1 2/3 scoreless innings while striking out a season-high three. In 11 appearances spanning 13 1/3 innings since his return to the majors, he has a 0.68 ERA, 12 strikeouts and two walks.

– Pedro Ciriaco continued his magic carpet ride, going 3-for-4 with a walk to improve to 7-for-13 (.538) since his recall. He also stole his second base.

– Nick Punto, pressed into duty when Gonzalez left the game, went 2-for-3 with a walk for his second multi-hit game in as many days.