Alexander will serve as the Giants' opening pitcher Sunday versus the Nationals, Susan Slusser of the San Francisco Chronicle reports.
Anthony DeSclafani had been listed as the Giants' probable starter, but he will instead operate in bulk relief. Alexander, 34, carries a 3.04 ERA, 1.01 WHIP and 15:6 K:BB in 26.2 innings (31 appearances) this season at the MLB level.