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It is all but certain the Houston Astros will not avoid losing their 100th game.

But doing so again Sunday may leave the Philadelphia Phillies digging out of a deeper hole than they expected over the final 15 games for the National League's second wild-card spot.

Philadelphia (73-73) rolled into Minute Maid Park on a seven-game win streak after sweeping a six-game homestand, figuring its momentum would continue against the major leagues' worst team. The Astros, however, have turned that theory on its head by taking two of the first three games of this series, including a 5-0 victory Saturday night behind a combined seven-hitter from Dallas Keuchel and four relievers.

"Tonight was unreal," Phillies manager Charlie Manuel said after his team went 0 for 10 with men in scoring position and stranded 12 baserunners. "We have to keep playing. We've got to play better. They outplayed us."

Despite the two losses to Houston, the Phillies remain three games behind St. Louis for the NL's final playoff berth, though they still need to overtake three other teams.

On Sunday, they must hope Roy Halladay (10-7, 4.01 ERA) can continue his late-season surge. The right-hander has won back-to-back starts and four consecutive decisions after grinding past Miami on Tuesday, giving up five runs and seven hits in 6 1/3 innings of a 9-7 victory.

Facing the Astros has been less stressful for Halladay, who is 2-1 with a 1.16 ERA and two complete games in four starts against them. He threw a six-hitter in his last outing at Minute Maid Park on Sept. 14, 2011, riding a first-inning run to a 1-0 victory.

Halladay will have catcher Carlos Ruiz back in the starting lineup after Manuel gave him Saturday off while he continues to fight plantar fasciitis in his left foot. Ruiz is 4 for 11 with three runs scored in five games since coming off the disabled list.

Houston (47-99) will try to win back-to-back games for the first time since Aug. 10-11 over Milwaukee and stave off its second consecutive 100-loss season for another day. After being held to three runs while dropping two of three to the Chicago Cubs, the Astros have scored 17 runs in this series -- equaling their total from the previous seven games.

"(Saturday) was the day where they all believed in themselves," Astros manager Tony DeFrancesco said. "(Sunday) is another day. If we can be the spoiler and give our guys some success and confidence, that's what we're looking for."

Houston's Jordan Lyles (4-11, 5.31) is out to win consecutive starts for the first time in his two-year career. The right-hander was efficient Tuesday versus Chicago, scattering two hits and two walks in five innings before five relievers finished up a six-hitter in a 1-0 victory.

Lyles did not get a decision in his only start versus Philadelphia, yielding three runs -- one earned -- in six innings of a 4-3, 10-inning defeat May 15.