Max Scherzer (12-5) was to start the second game for the Nationals and Matt Moore (3-12) for the Giants in a makeup of Friday night's rainout.
Giants manager Bruce Bochy said, "I don't know what happened really".
"He was in obvious pain and he was praying and I was praying, too", said manager Dusty Baker, adding that Harper would have an MRI. Jackson was charged with the loss in his last start as the Nationals fell 7-4 to the Cubs in Chicago on Saturday.
But the pitching of Jackson and hitting of Lind was overshadowed by the Harper injury. He had five by the end of the third inning Sunday.More news: Drunk American Assaulted After Giving Nazi Salute in Germany
But the game is unlikely to have an impact on the playoff race, as the Nationals lead the NL East by 14 1/2 games and the Giants are out of contention.
Should Strickland and Harper face off this weekend, it's unlikely that any fireworks would take place.
Giants: INF Orlando Calixte was recalled from Triple-A Sacramento as San Francisco's 26th player. Harper pulled a hard grounder that looked like an RBI double before it found Jones' outstretched glove. The All-Star has been sidelined since leaving his July 23 start at Arizona after two innings.
Justin Upton drilled a walk-off, two-run homer with nobody out in the bottom of the ninth inning to give Detroit a comeback victory that snapped Minnesota's six-game winning streak.More news: Silitch Sells 14897 Shares of Prudential Financial, Inc. (PRU) Stock
Giants players were already in street clothes talking to family and friends and walking toward the team buses before the game was announced as postponed. A bruise! Maybe Harper will be back out there in another week or two! . Baker said Bochy was the first one to call him when he was sacked by Cincinnati, and Baker called in April when Bochy had a heart procedure.
Harper is now one of the leaders in the NL MVP race and is hitting.326 with 29 home runs and 87 RBI.
There's a good chance Baker passes Bochy in this series.
Harper has been on the disabled list only twice in his career: In 2013, he missed 31 games with left-knee bursitis, and in 2014, he missed 57 games after having surgery on his left thumb.More news: Watch Pure Michigan 400 Online
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