Hisashi Iwakuma pitched eight sharp innings for Seattle, allowing one run on Brad Snyder's first career homer in the second and six hits. Charlie Furbush then got three outs to complete the six-hitter.
Iwakuma improved to 2-1 with a 1.61 ERA in three starts this month. The right-hander struck out six and walked one in his fourth start this season of eight innings.
Seager drove in Endy Chavez and Robinson Cano with a two-out double in the fifth inning, lifting Seattle to a 2-1 lead. The Mariners left a runner in scoring position in each of the first four innings.
Rangers starter Nick Martinez (1-4) allowed nine hits and walked one, but held the Mariners to two runs in six innings. The right-hander is 0-3 with a 9.45 ERA in his last three starts.
Seager added an RBI double in Seattle's three-run eighth. Dustin Ackley and Brad Miller also drove in a run in the eighth for the Mariners, who avoided being passed in the standings by the Rangers.
Seager has played well against the Rangers in his career, hitting .338 with 34 extra-base hits and 38 RBIs. Seager is hitting .396 (19 for 48) this season against Texas with three home runs and 12 RBIs.
NOTES: Mariners 1B Justin Smoak (strained quad), OF Corey Hart (strained hamstring) and OF Michael Saunders (shoulder inflammation) are close to being sent out on rehab assignments as they work their way back from stints on the disabled list, manager Lloyd McClendon said. The Seattle skipper said all three could begin a rehab assignment by week's end. ... Texas OF Leonys Martin occupied the top spot in the lineup for the second time in as many days on Sunday as the Rangers try to find a consistent leadoff hitter. Manager Ron Washington said that doesn't necessarily mean he has secured that role, though.