Martinez will play left field in Wednesday's game against the Twins, Christopher Smith of MassLive.com reports.
This will be Martinez's debut in a spring-training game, but he has participated in two controlled minor-league games. He homered off Rick Porcello on Monday and has five hits, three RBI and four walks in the two simulated sessions. While he'll be playing the field Wednesday, Martinez is expected to get most of his playing time as Boston's designated hitter.