Mervis was recalled from Triple-A Iowa and is batting eighth as the designated hitter Tuesday against the Astros, Matt Kawahara of the Houston Chronicle reports.
The 26-year-old was called up as expected Tuesday and will immediately make his way into the starting nine. Michael Busch has earned an everyday role at first base with his hot start to the season, so Mervis is likely to see most of his playing time at designated hitter, especially while Seiya Suzuki (oblique) remains sidelined.