Alex Bregman and Jose Altuve slugged their first home run of the years while Brandon Bielak produced 3 1/3 innings of effective relief in his major league debut as the host Houston Astros beat the Seattle Mariners 8-5 on Monday to claim a four-game series.Bielak (1-0), recalled earlier on Monday after ace right-hander Justin Verlander landed on the 10-day injured list with a forearm strain, retired the first eight batters he faced after entering in the fourth inning. The 24-year-old right-hander struck out Shed Long after surrendering consecutive two-out hits in the sixth, and he departed in the seventh after allowing a run-scoring groundout to Kyle Seager.Bielak allowed two runs (one earned) on four hits while striking out four without a walk. He delivered in a pinch for the Astros, who received three wobbly innings from right-handed starter Josh James. With the Houston rotation already stretched thin and their bullpen laden with youth, James allowed three runs on three hits and five walks with five strikeouts. He recorded just 39 strikes among his 75 pitches.Rookie first baseman Evan White staked the Mariners to a 3-0 lead with his first career home run, a two-run blast to left-center off James in the top of the third. The Astros rallied for four runs in the bottom of the inning against Mariners starter Kendall Graveman (0-1).Bregman capped the outburst with his 100th career home run, a three-run shot that plated Dustin Garneau and Altuve, whose RBI double had scored Kyle Tucker.