PITTSBURGH -- The Chicago Cubs lost 5-4 to the Pittsburgh Pirates in Game 1 of a doubleheader on Tuesday. Here is a quick look at the outcome.

How it happened: The winning run scored on a sacrifice fly in the eighth inning after Justin Grimm walked leadoff hitter Pedro Alvarez. Pinch runner Pedro Florimon then stole second and went to third on a bad throw by catcher Miguel Montero. The Cubs tied it 4-4 in the seventh on two wild pitches by reliever Joakim Soria allowing Starlin Castro and Tommy La Stella to score. Minutes earlier, La Stella came off the bench to deliver a run-scoring double and knock Pirates starter Gerrit Cole out of the game. The Cubs took a 1-0 first-inning lead after a stolen base and error allowed Dexter Fowler to reach third. He came home on a Chris Coghlan sacrifice fly. The Pirates responded with three in the bottom of the first as Cubs starter Jason Hammel wasn’t sharp. Andrew McCutchen and Travis Snider had the RBIs in the inning. Hammel lasted only 3 2/3 innings giving up five hits and three walks.

What it means: Back-end starting pitching concerns have popped up again as Dan Haren and Hammel were below average in back-to-back starts. Hammel is the much bigger concern, as he would be part of a playoff rotation. He has a 6.75 ERA in the first inning this season, after giving up three runs in the first inning Tuesday. Any progress he’s made this second half has been followed by a step backward.

The bullpen, led by Grimm, continues struggle in close games. His walks have hurt, and it’s not helping that Montero isn’t as sharp as he could be behind the plate. The winning runs over the past two games have come in part because of a wild pitch and a throwing error by the catcher.

The Cubs' magic number remains at 13, but they have fallen five games behind Pittsburgh for the first wild card in the National League.

What’s next: Game 2 of the series is Tuesday evening when Jon Lester (9-10, 3.50) takes on J.A. Happ (5-1, 1.79).