That is disappointing to manager Cecil Cooper, who said just before Wandy Rodriguez's 12-2 loss to the D-backs that good pitching was the key to their eight-game win streak.
Rodriguez lasted 2 1/3 innings, allowing three runs on two hits on Friday, and Brandon Backe gave up three home runs -- including two grand slams -- over 5 2/3 the following day.
Cooper said he did not have an explanation for what was going on with his rotation.
"I'm a big believer that you throw strikes," he said. "You pound the strike zone, just pound it. They do more picking at the zone than getting after hitters sometimes."
Rodriguez said after Friday's game that he was missing his location. He threw a total of 77 pitches, just 39 for strikes, while walking six.
Backe, who has had an up-and-down season on the mound, shining one game and tanking the next, said he just did not have a good pitch to throw in the 11-5 loss to Arizona on Saturday.
Neither he nor Cooper had an explanation for his inconsistency, but Cooper said when he was successful, he trusted his pitches and threw straight to batters.
"They need to get back to attacking that strike zone," he said. "That's the only way you can pitch to be successful if you look at in the long term. You pitch to guys, not away."
Wesley Wright, Geoff Geary, Doug Brocail and Jose Valverde are all available for Sunday.
Cooper said the starters need to trust their defense to back them up, calling the Astros fielders the best in the league. He also said it is not beyond the starters to pound the strike zone, they just have to get back to basics.
"Brian Moehler goes out there and throw strikes," he said. "We just have to have that mindset that we're going to go in, throw down over the plate, and let them hit it. My defense will help. I think that's the best formula. In the long haul you win."
Krysten Oliphant is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.