The 36-year-old Hill, the starter and losing pitcher in Game 2, will be pitching on short rest for the first time.
In Game 2, a 5-2 loss, Hill struck out seven over the first three scoreless innings, but Washington catcher Jose Lobaton slugged a hanging curveball into the wind for a three-run homer in the fourth inning.
Hill allowed three singles in the fifth inning and was removed after 4 1/3 innings, charged with four runs and six hits.
He was 5-2 with a 3.39 ERA for Los Angeles this season, and he has thrown a career-high 122 innings, 45 of them at Triple-A.
He will be available out of the bullpen in Game 5.