Iwakuma wins his season debut for Mariners
Starting pitcher Hisashi Iwakuma of the Seattle Mariners pitches on September 25, 2013 in Seattle, Washington - by Otto Greule Jr
Iwakuma missed more than a month at the start of the season with a torn extensor tendon in his right middle finger, but was activated hours before the game so he could take the mound.
The 33-year-old right-hander, who finished third in last year's American League Cy Young Award voting, allowed four runs on six hits while striking out three Houston batters on Saturday.
Iwakuma threw 56 of his 81 pitches for strikes and helped stake the Mariners to a 9-2 lead entering the seventh inning before the Astros rallied late.
Iwakuma, who went 14-6 with a 2.66 earned-run average over 33 starts last season, spent five seasons with Japan's Kintetsu Buffaloes and six more with the Rakuten Eagles before leaving his homeland after the 2011 season to join the Mariners.
The Mariners are off to a 13-15 start to the season while Houston has the worst record in the American League at 10-20.