Choo began the rally with a leadoff ground-rule double against Steve Cishek (1-2) and advanced to third on a fly-out by pinch-hitter Cesar Izturis. After Joey Votto was intentionally walked, Phillips lofted a fly to center to score Choo (3-for-4) with the decisive run.
Alfredo Simon (1-1) earned the victory with a scoreless top of the 13th.
Votto finished 4-for-6 with a solo homer and two RBI while Reds starter Bronson Arroyo yielded a pair of runs on six eights over eight innings.
The Marlins bullpen blanked the Reds for 8 2/3 frames after starter Wade LeBlanc had surrendered a pair of runs. Placido Polanco and Joe Mahoney each drove in a run for the Marlins.