The Reds tied the game on a ninth-inning home run by Jay Bruce, then escaped a two-on, one-out threat in the top of the 12th before ending the game one inning later.
Derrick Robinson reached on a one-out, infield single in the 13th off Vin Mazzaro (3-2) and took third on a base hit by Shin-Soo Choo. Joey Votto was walked intentionally to load the bases and Phillips followed with a shot up the middle to bring home Robinson.
Manny Parra (1-1), the last of six Cincinnati pitchers, worked the top of the 13th to get the win.
Pittsburgh's run came in the second inning and was brought home on an infield single by Russell Martin.