Tied at 3-3 entering the ninth and with Joe Nathan (3-2) pitching for Texas, Endy Chavez singled to center to start the inning. Humberto Quintero bunted to advance the runner, and Nick Franklin drew a two-out walk.
Seager then ripped an RBI double to right to give his team the lead.
Danny Farquhar pitched a 1-2-3 ninth to notch his seventh save. Yoervis Medina (4-3) gave up one run in the eighth but picked up the win.
Mariners starter Erasmo Ramirez gave up two runs -- one earned -- on three hits and a walk over seven frames. The 23-year-old right-hander remains unbeaten in six starts this season.
Rangers starter Yu Darvish, who was looking for his fourth consecutive win, gave up three runs on seven hits while fanning seven and walking four over 7 1/3 innings.
08/18 18:18:40 ET