Sanchez's double to deep center field with two outs came off Cardinals ace Adam Wainwright (1-1) and snapped a 1-1 tie.
The hit by the rookie reserve catcher scored Pedro Alvarez, who led off the inning with a walk, and was Sanchez's second game-winning hit of the week as he singled home the winning run in the 16th inning of Wednesday night's victory over the Chicago Cubs.
Tony Watson (1-0) retired all four batters he faced, striking out three, and ran his string of consecutive scoreless innings to 24, dating to last season. Jason Grilli pitched a scoreless ninth to convert his first save.
St. Louis managed just three hits.
Singed to a one-year, $5 million contract as a free agent in December, Edinson Volquez was sharp in his first start for the Pirates as he gave up one run and three hits in 5 2-3 innings with one walk and four strikeouts. That came after Volquez pitched two scoreless innings of relief Thursday against the Chicago Cubs.
Volquez's 5.71 ERA last season with the San Diego Padres and Los Angeles Dodgers was the highest among the 81 pitchers who qualified for the ERA title. He also allowed 15 runs in 13 innings in exhibition games this spring.
Wainwright went seven innings and allowed two runs and five hits after pitching seven scoreless innings in his first start of the season at Cincinnati in Monday's opener. He struck out seven and walked two.
An RBI triple by the Cardinals' Jon Jay in the sixth tied the score at 1-1 and chased Volquez.
NOTES: St. Louis CF Peter Bourjos, who is off to a 0-for-13 start with his new team, got the day off. Jay started in his place. The Cardinals acquired Bourjos from the Los Angeles Angels in an offseason trade. ... RHP Jameson Taillon, Pittsburgh's top pitching prospect, will undergo Tommy John surgery at a date to be determined with David Altcheck performing the operation in New York and he'll miss 12 to 18 months. ... The Cardinals play their home opener Monday against the Cincinnati Reds with RHP Michael Wacha (0-0, 0.00) facing LHP Tony Cingrani (0-0, 0.00). ... The Pirates are off Monday then open a three-game series Tuesday night at Chicago with RHP Charlie Morton (0-0, 0.00) pitching against Cubs RHP Edwin Jackson (0-0, 1.29).