Martinez (foot) will begin a rehab assignment with Triple-A Columbus on Friday, Tim Stebbins of MLB.com reports.
Martinez hasn't played since June 13 due to a broken left foot but will see five innings of action Friday. Martinez had been playing an everyday role in the outfield for the Guardians prior to his injury and has slashed .239/.276/.442 with 11 homers, 33 RBI, 28 runs scored, nine stolen bases and a 7:53 BB:K across 243 plate appearances this season.