Veteran utility man Michael Martinez was designated for assignment, giving the Indians 10 days to either trade or release him. If Martinez clears waivers, he could accept an outright assignment to the Minors.
Guyer is batting .182 with a .528 OPS through 21 games this season, and has struggled against lefties (.174 average and .507 OPS). He has been used primarily as a right fielder with lefties on the mound, given that he posted a 1.021 OPS off southpaws last season.
Robertson, 31, who was in Spring Training as a non-roster invitee, can provide outfield depth for all three positions.