Alexander will start Thursday's game against Arizona, Susan Slusser of the San Francisco Chronicle reports.
Alexander has fallen into a somewhat regular role as an opener recently, as Thursday will mark his third start since July 24. The 34-year-old lefty holds a solid 3.13 ERA and 0.98 WHIP through 31.2 innings on the year but will likely only remain on the mound for an inning or two.