Of the top 11 starters by FanGraphs' Wins Above Replacement measure, the Rangers have three of the top 11 starters in the American League this season. At 2.5 wins, Matt Harrison ranks sixth, Yu Darvish three spots behind with 2.2, and Colby Lewis 11th with 2.1 (despite now being on the disabled list).
As you might expect from that, as a team, the Rangers lead all of baseball in WAR generated from starting pitching at 9.4. Even Derek Holland and Neftali Feliz had been pitching like good middle of the order guys prior to getting hurt, and they were back end stuff on this squad. Roy Oswalt has already been worth 0.6 WAR in his two starts, the kind of average production most teams have to be fine with as their No. 2 starter.
Oh, Texas also leads in baseball in bullpen WAR, for the record.
In the interest of multiple data points, you can also glance at Baseball-Reference's version of WAR. FanGraphs uses FIP, estimating a pitchers' expected runs allowed using the "three true outcomes" (K/BB/HR). BR uses actual runs allowed adjusted for factors such as team defense. Anyway, it drops Lewis down to 16th, but that's still great -- or more like [expletive] incredible --- for the third best starter on a team. Meanwhile, Darvish remains 9th, and Harrison jumps up to fourth.
Remember when the Rangers couldn't find a pitcher to save their lives?