Gentry sustained a head and neck injury on July 24 while sliding into second base and was placed on major-league baseball's new seven-day DL on July 28. He returned to the club Wednesday after a five-day stint at Round Rock, but the Rangers did not reinstate immediately in order to keep an overworked bullpen fully stocked.
The Rangers have typically used the right-hand-hitting Gentry in left field against left-handed pitchers. He has batted .265 with five doubles and 39 RBIs in 39 games since being recalled on May 7.
O'Day was recalled on Saturday when Alexi Ogando departed on paternity leave.