Astros 4, Rangers 2: Jason Castro broke out of a slump by belting a grand slam as host Houston continued its dominance over Texas in the opener of a four-game series.

Collin McHugh (7-9) permitted two runs and struck out six over seven innings to remain unbeaten over his last six starts before Josh Fields pitched a scoreless eighth and Tony Sipp a perfect ninth to earn his second save. Jose Altuve, Chris Carter and Dexter Fowler each had a hit and scored a run as the Astros beat the Rangers for the eighth time in nine meetings.

Leonys Martin and Robinson Chirinos each had two hits and scored a run and Mike Carp had an RBI for last-place Texas, which dropped four games behind Houston in the AL West. Roman Mendez (0-1) took the loss in relief of Nick Tepesch after serving up Castro's slam.

The Rangers collected three hits in the first inning but managed only one run on Carp's double-play grounder before doubling the lead on Carp's sacrifice fly in the third that plated Chirinos. McHugh escaped further damage by fanning Adrian Beltre and Jim Adduci with runners at second and third.

Houston went ahead in the fifth when Altuve singled with one out and Carter walked, chasing Tepesch in favor of Mendez, who yielded an infield single to Fowler before Castro, who entered in an 0-for-20 rut, cranked a 2-0 fastball 420 feet into the seats in right. Texas appeared to get a run back on Rougned Odor's infield single in the sixth but he was ruled out upon video review.

GAME NOTEBOOK: Adduci came out of the game in the bottom of the fourth after tumbling over Odor and banging his back and head on the ground while catching an inning-ending foul ball. ... Astros LF Robbie Grossman was held out of the starting lineup with an ailing left ankle that he hurt in Wednesday's game. ... Rangers OF Alex Rios sat out his second straight game due to soreness in his right thumb but is expected back in the lineup Friday.