Bryce Harper left in pain Saturday. (Greg Fiume/Getty Images)

Nationals Park went silent in an instant. The thousands in attendance – so excited moments earlier to watch baseball after enduring a three-hour, one-minute rain delay — were in shock. Bryce Harper, the brightest star on a Washington Nationals roster full of them, was on the dirt behind first base holding his left knee in the first inning of the Nationals’ 3-1 victory over the San Francisco Giants on Saturday night. He was in agony and he was not getting up.

The all-star right fielder had just slipped across the base attempting to beat Giants first baseman Ryder Jones to the bag for an infield single with a lunge as his helmet flew off. When his left leg landed beyond the bag, it planted and buckled. He then soared through the air past the first-base umpire, landed on his right side and immediately grabbed his left knee when he hit the ground.

Harper remained there for a few minutes, writhing in pain. Hitting coach Rick Schu and trainer Paul Lessard then helped him off the field, with Manager Dusty Baker trailing. Harper didn’t apply any weight on his left leg, his head down as he limped off the field and through the Nationals’ stunned dugout.

After the game, Baker said Harper hyperextended his knee and will undergo an MRI on Sunday morning. A club spokesperson said the team will provide a further update then, before the Nationals and Giants begin a split doubleheader.

“He was in obvious pain, and he was praying and I was praying, too,” Baker said. “That what we usually do when things are in a bad way. The good thing is he’s young and strong. I’m very optimistic that he’ll be at least fine shortly.”

Harper’s injury was reminiscent of the scene in the same area behind first base on April 28, when Adam Eaton suffered a season-ending knee injury trying to beat out a groundball.

Harper’s left knee injury history in the majors is limited to a bursitis bout in 2013. He underwent surgery to remove the bursa sac in the knee the following offseason, but didn’t have any structural damage.

After Saturday’s game, he was seen walking out of the stadium with a slight limp.

“It doesn’t matter what team you’re on,” said Edwin Jackson, who allowed one run across six innings to get the win. “When you see a caliber player like that or any player go down like that, you hope for the best. And it’s fortunate that he’s up and walking. He’s definitely one of those guys you can’t replace on a team. It’s crazy, but it’s definitely great to see him up in spirit and walking around.”

The potential season-altering play occurred minutes into a game that started at 10:06 p.m. after ominous clouds, torrential downpours and lightning rammed the area. Major League Baseball, not the Nationals, decided if and when the game would be played because the Giants don’t return to Washington this season. The league deemed the conditions playable after the rain slowed from its earlier levels, announcing a start time of 10:05 p.m. at 9:22 p.m. The precipitation, however, continued through the first inning.

Last season, Nationals catcher Wilson Ramos suffered a torn anterior cruciate ligament following a rain delay less than two weeks before the start of the postseason. Baker admitted he thought about Ramos’s injury when Harper went down, but said he understood the league’s decision to play the game.

“You had to try to play the game.” Baker said. “This is their only time in with the unbalanced scheduled. So we were kind of at the mercy of the schedule.

For all of the Nationals’ injuries this season, and there have been plenty, they have been able to avoid anything catastrophic since Eaton tore his anterior cruciate ligament. The big boppers in the middle of the order have stayed relatively healthy. Trea Turner, Jayson Werth, and Michael A. Taylor have missed ample time, but their returns are looming. The top four in their starting rotation have avoided major problems, though Stephen Strasburg is one of Washington’s 11 players currently on the disabled list.

The club has overcome the slew of maladies to post the third-best record in baseball at 69-45 after Saturday’s win, relying on characters that began the season on the bench or in the minor leagues to provide boosts on the periphery. The expectation was the team would be whole again by Sept. 1, giving it enough time to gel and build momentum into the postseason.

But whether Harper, a leading NL MVP candidate and arguably baseball’s biggest star, will be around to fuel the playoff run in the heart of the order is now uncertain.

“We’re just hoping for the best,” Baker said.

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