Pirates 6, Cardinals 3: Pedro Alvarez slammed his 23rd homer with one out in the top of the 19th and Andrew McCutchen added a two-run single as visiting Pittsburgh outlasted St. Louis in six hours, seven minutes.

Alvarez drilled a one-out curveball from Barret Browning (1-3) over the fence in right-center field as the second-place Pirates moved two games ahead of the third-place Cardinals in the National League Central.

McCutchen’s two-out, bases-loaded single plated two more runs as the Pirates improved to 4-0 in extra-inning games this season.

Scheduled Monday starter Wandy Rodriguez (8-12) pitched the final two innings for Pittsburgh, which is one game ahead of the San Francisco Giants for the NL’s second wild-card spot.

The Pirates took a 3-2 lead in the top of the 17th on an infield single by Garrett Jones against Cardinals reliever Marc Rzepczynski. James McDonald, who delivered a one-out, pinch-hit single to center to get the uprising started, easily scored from third.

St. Louis responded with back-to-back singles by Yadier Molina and Skip Schumaker in the bottom of the 17th against Juan Cruz. After Rafael Furcal lined out, pinch hitter Tony Cruz hit a sacrifice fly to left to score pinch runner Ryan Jackson to re-tie the contest.

The Cardinals took a 2-0 lead in the fourth when Carlos Beltran smacked a two-run double into the right-field corner.

Pittsburgh tied the contest in the sixth with pitcher Jaime Garcia’s error on a bunt opening the door. The runs scored on Josh Harrison’s sacrifice fly and McCutchen’s infield single.

Garcia posted a career-high 10 strikeouts for St. Louis while making his first start since June 5 due to shoulder issues. Garcia didn’t walk anyone and was charged with two unearned runs and five hits in eight innings.

Pirates starter Jeff Karstens allowed just two runs and two hits in seven innings.

GAME NOTEBOOK: The previous longest game between the two squads was a 17-inning affair on August 2, 1982 when the Pirates won 4-2. … Cardinals 1B Allen Craig went 2-for-4 and is batting .405 during a nine-game hitting streak. … The Pirates placed OF Starling Marte (oblique) on the disabled list and recalled OF Jose Tabata from Triple-A Indianapolis. … St. Louis 3B David Freese went 0-for-8 to drop his August batting average to .169. … Pittsburgh’s Neil Walker hit into a double play in the 11th as a pinch hitter in his first action since dislocating his right pinkie finger on Wednesday. … Beltran stole three bases, one in the 14th inning and two in the 18th.