The start of the game was delayed 3 hours, 1 minute by rain Saturday and there was a light rain in the top of the first inning.
There has been no update on Harper's injury.
Harper flew in the air and appeared to be in agony as he hit the ground while clutching onto the front of his knee.
Harper had to be carried off after not being able to put any weight on the leg. His final season in the majors yielded uneven results, pairing an impressive 25 home runs with a less impressive.196/.257/.453 batting line in 362 PA.
Harper is now one of the leaders in the NL MVP race and is hitting.326 with 29 home runs and 87 RBI.
Harper was replaced by Andrew Stevenson, who took over in center field with Brian Goodwin moving to right. He played in 105 of Washington's first 113 games. McCutchen, meanwhile, reported his left knee felt "fine" Saturday and could return Sunday.
Harper is under contract through next season and can be a free agent in the winter of 2018.
Brewers get Walker • The Milwaukee Brewers agreed to acquire veteran second baseman Neil Walker from the Mets. Jonathan Villar, counted upon to be the regular second baseman after a big 2016 season at shortstop, has been mired in a season-long offensive slump.