Mayer is out of the lineup for Wednesday's game against the Brewers, Chris Cotillo of MassLive.com reports.
With southpaw Shane Drohan on the hill for Milwaukee, Mayer and fellow left-handed hitters Jarren Duran and Masataka Yoshida will be held out of the starting nine. Isiah Kiner-Falefa will replace Mayer at second base and will bat ninth.