CINCINNATI -- After a sizzling surge toward the top, the Pirates lost one that they really needed for a shot at the title.
The Pirates' NL Central chances were hurt when Todd Frazier had a tying two-run homer in the seventh inning and Ramon Santiago hit a grand slam in the 10th, powering the Cincinnati Reds to a 10-6 victory on Saturday.
Pittsburgh started the day a game behind first-place St. Louis and could have pulled into a tie with a win. The Cardinals lost at Arizona 5-2 later Saturday. Instead, it comes down to the final day of the regular season on Sunday.
Even if they fail to win the division title, the Pirates have already clinched at least a wild card and would host that game on Wednesday.
"Wonderfully crazy, like the season," manager Clint Hurdle said.
The Pirates will either host the Giants in the wild-card game, with the winner facing the Nationals, or open the division series at the Dodgers on Friday.
John Axford (0-1) walked Frazier to open the 10th and gave up Chris Heisey's single and another walk with one out. Left-hander Bobby LaFromboise relieved, retired Bryan Pena on a shallow fly out, then gave up Santiago's first career grand slam.
Dylan Axelrod (2-1) retired the side in the top of the 10th.
"We couldn't close it out in the seventh, which we've been pretty efficient at doing," Hurdle said.
For second year in a row, the Pirates are finishing the regular season in Cincinnati on a playoff surge. Last year, they swept a three-game series at Great American Ball Park to clinch home-field advantage in the wild card game, and then beat the Reds at PNC Park in that one, too.
The Pirates' latest push includes 13 wins in the last 17 games. The loss on Saturday stalled their climb toward the top -- they haven't been in first place since April 8 -- and gave the Cardinals some room.
The Reds snapped a club-record streak of 45 consecutive losses when they allowed at least six runs in a game. Their bullpen got its first win since the All-Star break -- Reds relievers are 1-17 over that span.
The Reds are 24-42 since the All-Star break. They'll at least tie the club record for fewest wins since the All-Star Game. The 1933 team won 25 for the previous mark.
Pittsburgh had to overcome a rare off-day by Francisco Liriano, who gave up five runs in five innings. It was only the second time in 14 starts since the All-Star break that he'd allowed more than two runs. He remained 0-5 career in the regular season against the Reds, although he beat them in the wild-card game last season.
"It just wasn't his top-shelf game," Hurdle said.
Liriano struggled to get his fastball where he wanted.
"I was trying too hard, I think," he said. "I was trying to make perfect pitches."
The Reds extended GM Walt Jocketty's contract for two years through the 2016 season. His status was the last major question heading into the offseason. Jocketty was elevated to the job in 2008.
Simon hit a grounder to second baseman Neil Walker in the second inning, jogged a few steps down the line and turned toward the dugout while the ball was still in play.
Mercer's 12 homers are the most by a Pirates shortstop since Pat Meares hit 13 in 2000. ... Harrison's 15-game hitting streak is the longest by a Pirate since Neil Walker hit safely in 17 straight in 2012. ... Simon was 12-3 when he was picked for his first All-Star Game. In 14 starts the rest of the way, he went 3-7.
Pirates: Catcher Russell Martin was out of the lineup with a sore left hamstring that began bothering him on Wednesday.
Reds: Center fielder Billy Hamilton was out of the lineup and won't play on Sunday, either, because of a concussion suffered on Wednesday. Hamilton leads all NL rookies in runs, hits, doubles, stolen bases and RBIs.
Pirates: Gerrit Cole (11-5) tries to extend his streak. The right-hander has won each of his last four starts.
Reds: Johnny Cueto (19-9) tries to become the Reds' first 20-game winner since left-hander Danny Jackson in 1988 and the first Reds right-hander since Sammy Ellis in 1965.