Manager Derek Shelton confirmed Keller will start Sunday's series finale at St. Louis, Adam Berry of MLB.com reports.
The 24-year-old received the start in Tuesday's intrasquad game, and he'll remain on the five-day schedule to begin the season. Keller made his major-league debut in 2019 and struggled with a 7.13 ERA in 11 starts, but he made a concerted effort during the shutdown to increase the spin efficiency on his fastball, which theoretically should help him miss more bats.