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: Child rescuer amongst 7 dead in Syria shooting
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: Congress seeks UP CM Yogi Adityanath's apology over Gorakhpur deaths
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: Fourth Summer Signing: Mourinho Reveals The Type Of Player He Wants Bring
- Four-midable Manchester United sweep West Ham aside in Premier League opener
- ASEAN, Japan, China, S. Korea agree to bolster financial cooperation
- AK Steel Holding Corporation (AKS) Lifted to Hold at Zacks Investment Research
- Alexandre Lacazette starts for Arsenal in season curtain-raiser against Leicester
- Tom Cruise injured while doing a stunt for 'Mission Impossible 6'
- North Korea tensions mount over tough new sanctions at Manila meeting
- English-fluent new Foreign Minister Kono makes worldwide debut at ASEAN gathering
- Central Intelligence Agency chief says 'nothing imminent' in US-N.Korea standoff
- Amazon is issuing refunds to customers who purchased suspect solar eclipse glasses
- English-fluent new Foreign Minister Kono makes global debut at ASEAN gathering