The A's made the moves before Saturday's game in Seattle. Gentry was not in the starting lineup, but was available coming off the bench.
Gentry had been out with a lower back strain since late March. He did not play in a major league game during spring training. He started his rehab assignment at Class-A Stockton last Saturday, playing one game for the Ports before appearing in two games at Triple-A Sacramento.
Fuld started the last four games in center field with Coco Crisp slowed by a sore wrist. Fuld had a solid opening homestand but was just 2 of 17 on the A's current road trip.