Walker (10-7) suffered a cramp in his right hip flexor after working 6 1-3 innings. Walker, who struck out six, experienced discomfort while facing Chicago’s Adam LaRoche and walked off the field under his own power after being examined by a team trainer.
Tom Wilhelmsen pitched the ninth to earn his fifth save in as many opportunities.
The Mariners snapped a scoreless tie in the sixth with two solo home runs. Seager, who entered Friday’s game hitting .196 in August, led off the inning with a homer to right off White Sox starter John Danks (6-12).
Two batters later, Gutierrez drove his homer to left, giving Seattle a 2-0 lead.