The Nationals didn't need long to take their first lead of the series in Chicago.
After going three up, three down in the first, Adam LaRoche led off the second with a single and Ryan Zimmerman doubled to left off Jason Hammel to give the Nats a 1-0 advantage over the Cubs.
Zimmerman reached third on the throw and Wilson Ramos walked to put runners on the corners. But Zimmerman was thrown out at home when aggressively trying to score on Ian Desmond's fielder's choice grounder.
Desmond and Ramos moved up second and third on a wild pitch the next at-bat, but were stranded there when Danny Espinosa struck out and starter Tanner Roark grounded out.
The lead was short-lived as the Cubs scored twice off Roark in the bottom of the second to take a 2-1 lead.
Luis Valbuena led off the second with a double. Chris Coghlan's infield single didn't advance the runner. But John Baker's RBI single to center scored Valbuena to tie the game and moved Coghlan to third. Coghlan scored for a 2-1 lead on Darwin Barney's RBI single to center.
So Roark, an Illinois native making his first career start at Wrigley Field, has allowed two runs on five hits in two innings. He has struck out one and walked none. But this could be a short outing if he doesn't settle down, as the right-hander has already thrown 51 pitches, 38 for strikes.
Update: LaRoche tied the game at 2-2 when he led off the fourth with a homer into the netting in right field.
It was LaRoche's 10th homer of the year and his ninth career blast at Wrigley Field.
Hammel has allowed two runs in four innings.
Update II: The Cubs reclaimed the lead at 4-2 by scoring twice in the bottom of the inning.
Coghlan and Baker singled to start the fourth. Barney's groundout moved both runners up a base. Hammel struck out swinging for the second out.
But Roark couldn't get out of the jam, as Ryan Sweeney drove a two-run single into center field.
Roark has now allowed four runs on nine hits in four innings, striking out two and walking none. It marks the first time the right-hander has allowed more than three runs since May 3, snapping a streak of nine straight starts holding opponents to three or fewer. Roark posted a 1.89 during that stretch.
So far today, he has thrown 76 pitches, 56 for strikes.
Update III: Roark's day is done after he gave up four runs on a season-high 10 hits. He finished with two strikeouts and one walk.
Roark threw 101 pitches, 72 for strikes.
Left-hander Jerry Blevins is on in relief with the Nats still trailing 4-2 in the seventh.
Update IV: The Cubs broke the game open in the seventh.
They loaded the bases with one out on a Justin Ruggiano double and two walks. Blevins struck out Coghlan for the second out and Baker hit a bases-clearing double to right for a 7-2 lead.
Aaron Barrett relieved Blevins and struck out Barney to end the inning, but the damage was done.
Blevins finished with three earned runs on two hits, two walks and a strikeout in just two-thirds of an inning. With that one outing, the lefty's ERA jumped from 4.50 to 5.34.
Update V: The Nats will now need to sweep Saturday's doubleheader to leave Chicago with a series split after absorbing a 7-2 beating at the hands (paws?) of the Cubs.
Roark's so-so start results in him falling to 7-5. Hammel improved to 7-5 by holding the Nats to two runs in 6 1/3 innings.
Washington managed just seven hits in the loss. They went 0-for-4 with runners in scoring position.
The Nats slip to 41-38, meaning the Braves have a chance to draw even for first place in the division with a win over the Phillies tonight.