This time the Diamondbacks were the ones being beaten.
It was the third walk-off win in as many days for NL-East leading Washington, the first two coming against the Pirates.
“They don’t come around very often that’s for sure,” Williams said, “but (we) just keep fighting.which is a great trait to have.”
LaRoche sent a 3-1 pitch from Will Harris (0-3) off the wall in the back of the Nationals bullpen and was mobbed by his teammates at home plate.
“I got every bit of it, I did,” LaRoche said. Just a crazy few days. I don’t know how we’ve gotten these walk off situations the last few days, but we have and have been able to grind back.”
It was LaRoche’s first career walk-off homer.
“Nice to get my first one, it took me long enough,” the 34-year-old said.
Winning pitcher Craig Stammen (3-4) pitched out of a bases-loaded, no outs jam in the top of the inning.
“We missed our opportunity, me striking out instead of putting the ball in play,” said Didi Gregorius, who made the second out against Stammen.
Arizona tied it 4-4 when David Peralta led off the ninth with a solo homer off Tyler Clippard.
Washington trailed 3-2 when Denard Span doubled with one-out in the eighth against Brad Ziegler and Anthony Rendon followed with a triple to tie it. Jayson Werth then scored Rendon with a sacrifice fly.
Miguel Montero had three hits for Arizona, and rookie Ender Inciarte extended his hitting streak to 18 games.
Arizona had taken the lead in the top of the eighth.