Justin Masterson has been perhaps the biggest surprise for the Sox, allowing only 29 hits in 42 innings and holding opponents to a .195 batting average in posting a 3-1 record and a 3.43 ERA.

The Providence Journal / Mary Murphy

The Boston Red Sox have hit the numerical halfway point. It's been a half season characterized by young pitching and injuries.

They’ve been able to cobble together this record despite missing David Ortiz for a month and counting because of a serious wrist injury.

In addition to other assorted injuries across the roster the team has won with a starting rotation featuring two rookie pitchers ( Clay Buchholz and Justin Masterson) and another one ( Jon Lester) with little more than a year of big-league service time.

The kid pitchers aren’t the only fill-ins who have stepped up. Brandon Moss, Sean Casey, Kevin Cash and Coco Crisp — whose status was in question when the season began, as it appeared he might lose his center-field job to Jacoby Ellsbury — are among the others who have done well when pressed into service.

But the pitching staff has been especially hard-hit. Curt Schilling, of course, won’t throw a pitch all season. Josh Beckett had a back problem in spring training and wasn’t 100 percent when the campaign began. Bartolo Colon began the year on the disabled list and is back there now. Daisuke Matsuzaka just returned after his own three-week stint on the DL.

Yet the Sox are still fifth in the American League in team earned-run average (3.81). Their starters have 36 wins, the second-highest total in the league. The staff leads the league in strikeouts, with 602. Their pitching has been superb.

And the youngsters have been a huge part of it all.

Lester has been especially effective, pitching more like a No. two starter than a back-end-of-the-rotation guy, which is where the Red Sox might have seen him heading into spring training.

The left-hander, his cancer issues and recovery behind him, vaulted into the national public’s consciousness by throwing a no-hitter against Kansas City on May 19. But his emergence as a confident strike-thrower began a few starts earlier, when he limited Toronto to one hit in eight shutout innings on April 29.

Counting that outing, Lester has gone 5-1 with a 2.13 earned-run average. He has walked only three batters over his last four starts, totaling 27 2/3 innings, and has issued no more than one base on balls in any of those games.

When Buchholz faltered a bit and was sent to the disabled list with a split fingernail, a convenient situation that allowed the Sox to send him down to refine his craft, Masterson stepped in and showed poise and big-league stuff. Masterson is 3-1 with a 4.25 ERA in five starts since being called up from the minors for a third time, on June 3.

In the bullpen, Craig Hansen has shown flashes of brilliance with his fastball and slider while Manny Delcarmen has blossomed into a dominant power arm, helping to offset the inconsistency of Hideki Okajima by forming a strong bridge to closer Jonathan Papelbon.

Delcarmen is unscored upon in his last 11 outings, totaling 12 2/3 innings. The right-hander has 15 strikeouts over that stretch.

The Sox’ ability to plug in a Masterson or a Hansen without missing a beat is a feather in the organization’s cap and a reason Boston is on track for another trip to the playoffs, with a chance to defend its World Series title.

Not that it will be an easy road in the A.L. East. Tampa Bay is loaded with talented youngsters, notably on the mound, and the New York Yankees always seem to be lurking.

But a lot should be said about Boston’s resilience, depth and blend of youth and experience while the Rays’ pitchers have to prove they can shoulder the load in August and September when the innings pile up and the pressure is ratcheted up. The Yankees? They can’t be written off, either.

The Sox aren’t necessarily a dominant team from top to bottom. But as the second half dawns, they appear to be better than anyone else, or at the very least just as good as the Los Angeles Angels of Anaheim, the Yankees, the Rays and any contending team in the A.L. Central.

skrasner@projo.com