Martinez (back) will serve as the Red Sox's designated hitter and bat cleanup Sunday against the Astros, Pete Abraham of The Boston Globe reports.
Martinez returned from a four-game absence to start in Friday's series opener, but his ongoing back issue resulted in him checking out of the lineup during Saturday's 4-3 loss. The Red Sox still made the slugger available off the bench for that contest, and he came in to deliver a two-out walk as a pinch hitter. After incurring no setbacks following the appearance, Martinez received the green light to fill his usual DH duties in the series finale.