HOUSTON -- The Astros had established such a comfort in the reliability of their high-leverage relievers that little could prepare them for what unfolded on Friday night against the Angels.

Right-handers Luke Gregerson and Ken Giles, half of the Astros' quartet of rock-solid relief pitchers (a group that also includes right-handers Chris Devenski and Will Harris) combined to cough up a three-run lead in a 10-6 loss that severely damaged the Astros' playoff aspirations. Gregerson allowed a run on two hits in the eighth inning; Giles blew his fifth save by coming apart at the seams in the ninth.

Giles surrendered six earned runs on three hits and three walks, inflating his ERA from 3.47 to 4.31 in the process. With eight games remaining in their season and their deficit for the second American League wild card now 21/2 games behind the Tigers, the Astros were left floored by the development involving Giles in particular.

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"Toughest inning of the year," Astros manager A.J. Hinch said. "For a lot of reasons."

Added Giles: "I didn't do my job. Didn't make my pitches. That's all I can say. I just didn't do it."

The Astros (81-73) have lost twice as many games to the Angels (68-86) over the first two games of this series than they did in the first 12 meetings between the teams this season. At best, they can salvage a split of the four-game set with victories on Saturday night and Sunday.

Right-hander Brad Peacock (0-0, 2.86 ERA) will make his fourth start for the Astros in the third game of the series. Peacock, who has filled in admirably for injured left-hander Dallas Keuchel (left shoulder inflammation), is 3-0 with a 4.50 ERA in five career games (three starts) against the Angels. He has not pitched against Los Angeles this season.

Angels right-hander Jhoulys Chacin (4-6, 5.26 ERA) will make his 33rd appearance and 21st start of the season. Chacin is 1-2 with a 4.50 ERA in five career games (four starts) against the Astros, including 0-1 with a 9.00 ERA in two games this season.

Chacin, who will make his 16th start for the Angels, has toggled between the rotation and bullpen for the Angels, rejoining the rotation on Sept. 14 against the Mariners after making four appearances out of the bullpen between Aug. 27 and Sept. 10. In his last four starts for the Angels, Chacin has pitched to a 0.87 ERA.

"I think Jhoulys has the ability to do both," Angels manager Mike Scioscia said. "He's done very well out of our pen and recently with some adjustments that he's made he's been very effective as a starter. I think his upside is still as a major league starter and I know that's what he wants to do and I think he can be effective doing that but if not he's shown he can throw out of our bullpen."