Atlanta placed O'Day on the 15-day injured list Wednesday with a strained left calf muscle.
Atlanta will swap one right-handed reliever off the IL for another, as closer Kenley Jansen (irregular heartbeat) was reinstated to the active roster in a corresponding move. Though injuries had marred three of his past four seasons, O'Day had been in good health during his age-39 campaign before the calf issue surfaced. In 28 appearances out of the Atlanta bullpen, O'Day has picked up two wins and six holds while turning in a 4.15 ERA, 1.34 WHIP and 26:10 K:BB across 21.2 innings.