The Angels designated Martinez for assignment Saturday.
Martinez was optioned to Triple-A Salt Lake on May 14 and has now been designated for assignment. The 24-year-old slashed just .189/.308/.369 with six home runs and 14 RBI in Triple-A this season. His spot on the 40-man roster will be taken by Gustavo Campero (hand), who was elevated from Double-A Rocket City on Saturday and placed on the 10-day injured list.