The Nationals were down, 4-3, in the ninth inning when they rallied off closer Jeanmar Gomez. After Bryce Harper and Danny Espinosa reached on singles and Clint Robinson walked to load the bases, Werth drove a 2-2 pitch up the middle, scoring Harper and Espinosa to end the game.
Werth said he had trouble tracking the ball in the late-afternoon shadows.
"The shadows set in pretty good. It was tough to see," Werth said. "The first pitch I was taking all the way. I was trying to see if I could pick up an arm slot. I was really struggling to see until about the third pitch. I had an idea of where the ball was coming. Luckily, I got into a count and [Gomez] made a good pitch, 2-1. He stayed with the fastball. I was surprised. The guy has a good off-speed pitch. He has a good changeup and slider. I smacked [the fastball] up the middle."
The walk-off win completed a three-game sweep for the Nationals, who chased Werth into right field in celebration. There was manager Dusty Baker doing his hop, skip and a jump in front of the dugout after the winning run scored. Werth was then doused with Gatorade twice.
"You are just glad it didn't happen on the road," Baker said. "No matter what he is doing or how he is playing, Jayson has been a clutch man all these years. A clutch man knows how to come through."