The Nationals' offense didn't register a hit until the fourth inning -- a bloop single to left by Adam LaRoche. Washington wound up loading the bases, but Rick Ankiel struck out swinging to end the frame.
Ramos led off the fifth with his third homer of the year -- a 409-foot shot to straightaway center off Cincinnati starter Mat Latos -- to tie the game at 1. Espinosa followed suit in the sixth with a 379-foot homer to right.
Ramos, however, injured his right knee while chasing a passed ball in the bottom of the seventh. He was helped off the field and replaced by Jesus Flores.
"Losing Willy is a big, big blow," Washington manager Davey Johnson said afterward. "I don't know how bad it is. He's going for an MRI, but I've got a bad feeling he tore something. We'll just keep our fingers crossed."
Zimmermann, meanwhile, entered the night 1-3 despite a 2.29 ERA but had pinpoint control throughout. After a 23-pitch first inning, he allowed just two hits -- both infield singles -- over the next three innings. The Reds' only real threat came in the first when Zack Cozart and Drew Stubbs were called safe on bang-bang plays at second and first, respectively, as Espinosa tried to turn a 6-4-3 double play. Zimmermann, however, induced groundouts from Joey Votto and Brandon Phillips to limit the damage to one run, and a called third strike on Jay Bruce brought the inning to a close.
"After the first inning there, I thought I was going to have a short outing," Zimmermann said. "But I had to buckle down and get some quick outs."
Zimmermann pitched through the seventh, Tyler Clippard pitched a scoreless eighth, and Henry Rodriguez struck out the side in the ninth.
"Their pitchers are dealing," Reds manager Dusty Baker said. "They've dealt on us most of the year -- and the rest of the league."
Latos, on the other hand, cruised through the first three innings, but labored in the fourth and fifth. He allowed one run on three hits, but needed 109 pitches to get through five innings and tied his career high with five walks (one intentional).
Phillips gave the Reds a 1-0 lead on an RBI groundout that plated Cozart in the first inning, and later robbed Bryce Harper of an RBI hit in the fifth. The Reds intentionally walked LaRoche to load the bases for Harper with two outs. Harper sent a ball up the middle, but Phillips ran toward the center-field grass, gloved the ball, and then flipped it behind his back with his right hand to Cozart for the force play to end the inning.
Harper, who needed 10 stitches above his left eye following a [self-inflicted] bat incident in the Washington dugout Friday night, started in right field and hit fifth in the order. He finished 0-for-4 and has one hit in his last 19 at-bats.
Washington, however, got the last laugh, as Cincinnati went scoreless over the final eight innings.
"We just didn't get key hits; that's basically it," Phillips said. "We had opportunities to come through, but we just didn't get it done. [Zimmermann's] a great pitcher, but every pitcher makes mistakes. He made a lot of mistakes today, but we just didn't do anything about it."
The official attendance was 42,294 -- making it the second-largest non-Opening Day crowd in Great American Ball Park history. GABP opened in 2003.
The Nationals will go for the series sweep Sunday. They are 5-1 against the Reds this year, with three one-run victories.