Lopez entered Saturday with a 3-0 record and a 1.83 ERA and hadn't issued a walk in 19 2/3 innings pitched this season, while striking out 14 batters. He's thrown more innings than any other pitcher in the Major Leagues without issuing a walk.
"He's thrown the ball extremely well and he's back throwing exactly how he did in 2010, when he came up and really burst onto the scene and threw the ball real well," Astros manager Brad Mills said. "He's just doing a great job, and when we can rely on a guy to come in and do that type of job, that's pretty impressive."
Lopez, who has stranded seven of eight inherited runners this season, walked just five batters in 67 innings in 2010, making him the only player in the Majors to walk five or fewer hitters while pitching more than 50 innings. Only four pitchers have done that since 1959.
Last year, he walked 18 batters in 71 innings, while going 2-6 with a 2.79 ERA.