The good news for the St. Louis Cardinals is that they still have nine games left against the Pittsburgh Pirates. However, the bad news is that they will be trying to avoid a five-game sweep to the Pirates on Thursday when they close out the set from PNC Park.

Pittsburgh stretched its lead atop the National League Central to 2 1/2 games over St. Louis on Wednesday with a thrilling win, as Russell Martin came through with a tie-breaking single in the bottom of the eighth inning to lift the Pirates to a 5-4 come-from-behind win.

Martin, Neil Walker and Clint Barmes each finished with two hits and an RBI to help Pittsburgh twice battle back from two-run deficits, while the bullpen turned in five scoreless innings to offset an uncharacteristic rough outing from starter Jeff Locke.

The Pirates have now taken the first four tests of this critical five-game set between the NL Central's top two clubs and won five of six overall.

"It feels great ... but there's still a lot of baseball left," Walker said.

St. Louis, on the other hand, was dealt its seventh consecutive defeat after failing to hold on to a 4-2 lead after 3 1/2 innings. It's the Cardinals' longest losing streak since a seven-game slide during June of their eventual 2011 World Series championship season.

The Cardinals will also have to deal with the absence of Yadier Molina for at least the next two weeks, with the team placing the All-Star catcher on the disabled list prior to the contest due to a strained right knee.

Matt Holliday went 3-for-5 with two RBI and Carlos Beltran had a pair of hits and two runs scored for St. Louis, but Trevor Rosenthal (1-2) was reached for a run on two hits after taking over for Adam Wainwright to start the bottom of the eighth.

St. Louis has managed just one home run in 13 games since the All-Star break.

Another loss on Thursday would ensure the first sweep of the Cardinals in a series of at least five games since the New York Giants took six in September, 1916.

Pittsburgh's last five-game sweep came against the San Francisco Giants in September of 1996.

Getting the call for the Pirates on Thursday will be righty Charlie Morton, who has won his last two starts. Morton beat the Miami Marlins on Saturday, despite giving up four runs (3 earned) and nine hits in five innings. He also struck out six without walking a batter and improved to 3-2 to go along with a 3.59 ERA.

Morton has allowed 18 base runners over 11 2/3 innings in his last two starts, but has walked away with a win in each outing.

Morton has struggled against the Cards in his career, posting a 2-7 mark with a 6.17 ERA in 11 starts.

St. Louis, meanwhile, will turn to 25-year-old righty Joe Kelly, who is 1-3 with a 3.44 ERA. Kelly did not get a decision on Saturday against the Atlanta Braves, but was terrific, as he scattered seven hits over 6 1/3 scoreless innings in his team's 2-0 loss.

"Very, very impressive," Cards skipper Mike Matheny said. "It was maybe the best I've ever seen him throw. Everything. His aggressiveness, his slider, breaking ball, changeup; all of them were as good as I've seen."

Kelly is 0-2 with a 6.43 ERA in five games (1 start) against the Pirates.

St. Louis is just 1-5 in the Steel City this season and has lost six straight overall to the Bucs.