CHICAGO -- Francisco Liriano tiptoed along a tightrope for five innings. In the sixth, the Chicago Cubs knocked him off.
Darnell McDonald's three-run home run in the sixth sent the Pirates to a 4-2 loss Wednesday afternoon at Wrigley Field, preventing them from sweeping the Cubs and clarifying their to-do list for the weekend.
Cubs starter Jake Arrieta kept the Pirates from threatening on offense for his six innings, and three Cubs relievers followed suit despite a ninth-inning charge.
Furthermore, the Pirates could not take advantage of the Cubs' fielding or baserunning issues which included two errors by shortstop Starlin Castro and two other misplays.
To have any shot at winning the National League Central Division, the Pirates will need the Cubs to help them out.
Only a Cubs sweep of the Cardinals in St. Louis this weekend and a Pirates sweep of the Reds in Cincinnati would pull the Pirates and Cardinals into a tie for first place and set up a 163rd regular-season game Monday at PNC Park to determine the division champion.
Short of that, the task is simple -- win the series against the Reds and the one-game wild-card game takes place Tuesday at PNC Park.
The Cubs hit Liriano (16-8) well Wednesday, but for most of Liriano's outing he limited the damage. In five-plus innings, Liriano allowed four runs on eight hits and struck out eight. The second Cubs batter scored, and the Cubs put a runner in scoring position in each of the first four innings.
Twice, Liriano struck out two batters in a row to end the threat.
"They fouled off a lot of good pitches," Liriano said. "I made a couple mistakes too, left a couple pitches up."
Darwin Barney hit a ball into shallow right-center field in the first. Andrew McCutchen bobbled it, Barney never stopped running and was safe at second with what was generously ruled a double. McCutchen's bobble burned the Pirates on the next at-bat, when Anthony Rizzo's single scored Barney to give the Cubs a 1-0 lead.
"The command was just enough off," manager Clint Hurdle said.
"The swings and misses were there. Some of the weak ground-ball contact that we normally see, balls were fouled off. He just wasn't quite as sharp."
Liriano survived the next four innings even though Cubs reached third twice. But nobody scored, and Liriano retired the side in order in the fifth.
"Just executing pitches, not trying to do too much, trying to hit my spot and let them hit the ball, put it in play," Liriano said.
A single and a walk, the only one he issued all day, put two on with nobody out in the sixth for McDonald.
Liriano had allowed two doubles to McDonald in his first two at-bats, so pitching coach Ray Searage went to the mound to discuss the situation.
McDonald jumped on a 2-1 fastball for a three-run homer, his first this season, and gave the Cubs a 4-1 lead.
"The last pitch, I tried to go in, and it stayed right down the middle," Liriano said.
A mixture of aggression and patience helped the Pirates tie the score in the third. Starling Marte singled with two outs, his second hit, and stole second. Neil Walker reached first on an infield hit, sending Marte to third.
Arrieta walked McCutchen and Justin Morneau to force Marte home and tie the score, 1-1.
As quickly as the Pirates created a scoring chance in the fourth, they squandered it.
Pedro Alvarez smoked what should have been a hard line-out to Castro at short. But Castro whiffed on the catch and the ball screamed into the left-center field gap.
Neither Junior Lake nor Ryan Sweeney fielded it with any expediency and nobody covered third, so Alvarez motored to third on a three-base error.
After one out, though, Alvarez found himself doubled off third when Clint Barmes lined out to third baseman Donnie Murphy and the inning ended.
A ninth-inning rally gave the Pirates a chance.
Tony Sanchez reached first on an error and Felix Pie pinch-ran for him.
Pinch-hitter Jose Tabata tripled to score a run. Cubs closer Kevin Gregg then struck out Marlon Byrd and Marte to end the game.
Bill Brink: email@example.com and on Twitter @BrinkPG. First Published September 25, 2013 6:00 PM