The Phillies have a 2-1 lead in the best-of-five series and can advance to the NL Championship Series with a Game Four win on Wednesday in St. Louis.
Francisco broke open a scoreless game with a three-run homer in the seventh inning off Cardinals starter Jaime Garcia to make a winner out of Philadelphia starter Cole Hamels, who had yielded his turn at bat to Francisco.
The Cardinals fought back with a run in their half of the seventh, a run-scoring single by David Freese, and another in the ninth on an RBI-single by Yadier Molina.
Phillies reliever Ryan Madson registered the final five outs for the save and retired a red-hot Ryan Theriot, who had gone 4-for-4 in the game, on a grounder to second base to end it.
Starter Garcia had been mowing down the Phillies before a tactical move backfired on the Cardinals.
The 25-year-old Mexican gave up a lead-off single in the seventh to Shane Victorino, who moved up to second base on a passed ball.
With first base open and two outs, Garcia intentionally walked No. 8 hitter Carlos Ruiz and Phillies manager Charlie Manuel countered by sending Francisco to pinch-hit for Hamels.
Garcia left a 1-0 pitch up and over the plate and Francisco crushed a line drive that cleared the left-field fence for all the runs the Phillies would need.
“I thought it was going to be a double, then saw it bounce over the fence, and just pure excitement and pure joy,” said Francisco.
St. Louis out-hit Philadelphia 12 to seven, including four hits by Albert Pujols, but stranded 14 men on base.
“They had base runners every inning,” said Phillies manager Manuel. “You feel like when you get in situations like that you’re dodging bullets. We were dodging most of the game.”
Part-time outfielder Francisco, however, fired the killing shot.
“In my role you kind of picture yourself there in a big situation as a pinch-hitter,” he told reporters. “You try and come through for your team.
“It was pretty exciting coming around the bases and celebrating with the guys. But we have to come back and win one more game.”
The series resumes on Wednesday in St. Louis. A Phillies win would put them into the NL Championship Series for a fourth consecutive year while a Cardinals win sends the series back to Philadelphia for a decisive fifth game.
Roy Oswalt (9-10) will start Game Four for Philadelphia, while Edwin Jackson, who was a combined 12-9 for the Chicago White Sox and Cardinals, takes the hill for St. Louis.
The winner of this series faces either Milwaukee or Arizona, with the Brewers leading their series 2-0.
