Jordan Zimmermann has one of his better career outings against his nemesis St. Louis, allowing just one earned run over seven innnings at Nationals Park. (Mitchell Layton/Getty Images)

The sellout crowd at Nationals Park thundered. The closer teetered. The manager felt secure in a brazen, principled decision. And Bryce Harper, the superstar the moment yearned for, sat in the Washington Nationals’ dugout, a bystander as his turn in the lineup came up.

“Man, it’s tough to watch,” Harper would say later. “Being able to be up there in that situation is something that I thrive on and I want to be in.”

Harper watched the Nationals’ last-gasp fizzle without him for a reason that will be debated all year, one that could produce ripples that last all season. Manager Matt Williams yanked Harper from the Nationals’ 4-3 loss to the St. Louis Cardinals on Saturday afternoon for “lack of hustle” and “the inability to run 90 feet” after Harper failed to reach first base on a groundball back to the pitcher in the sixth inning. The rookie manager stood behind his decision even after Harper’s spot in the lineup came up during a ninth-inning rally that fell one run short.

It could have been Harper batting with one out in the ninth after Trevor Rosenthal balked two runners into scoring position. Instead, in his 18th game on the job, Williams had drawn a line in the sand.

“We made an agreement,” Williams said. “He and I made an agreement. This team made an agreement that when we play the game, that we hustle at all times, that we play the game with intensity and the willingness to win. As it turned out, his spot came up. Kevin Frandsen put on a nice at-bat against Rosenthal. But his spot came up with the ability to win the game. That’s a shame for his teammates.”

Harper, at 21 still the youngest player in the majors, said he “absolutely” understood Williams’s decision and “I respect what he did. It’s part of the game.”

The man who hired Williams backed the first-year manager with zero ambiguity.

“I unequivocally support the manager’s decision 100 percent,” General Manager Mike Rizzo said.

Harper had been dealing with tightness in his quad, which sidelined him Wednesday night in Miami. Harper said he’s “fine” physically and the injury did not prevent him from running to first base. Williams said the incident will be forgotten, and Harper will return to the lineup Sunday. He also had no regrets.

“It’s the way we set out to do it,” Williams said. “Regardless of situation, regardless of what’s happening to you personally, we have to play the game a certain way to give ourselves the best chance to win. And it’s too bad that it came down to that situation in the ninth inning, when he could have been at the plate. For the sake of his teammates and the sake of the organization, he needs to play with aggression.”

Leading off the sixth inning, Harper tapped a fastball back to Cardinals pitcher Lance Lynn, who snared it on a letter-high hop. Harper jogged out of the batter’s box, peeled off halfway to first base and headed for the dugout steps. Once he returned to the bench, Harper said, Williams informed him, “Kevin’s going to left.”

Williams cited the new, stricter enforcement of the transfer rule as one reason why Harper’s failure to reach first base upset him so much.

“He’s an exciting player,” Williams said. “People come to pay money and watch him play and watch him play the way he can play. And it’s pretty exciting. It’s pretty dynamic. But there’s another side to it. The other side is, regardless of how the ball comes off the bat or regardless of how he’s feeling about an at-bat, he must maintain that intensity and that aggressiveness. And that means running all the way to first base and touching the base.

“There’s a million reasons why. The transfer rules that we’ve seen lately. What if that guy bobbles the ball as he’s throwing it around? If he doesn’t touch the base, he’s out. If he’s in the dugout, he’s automatically out. Beyond all the just-run-90-feet stuff, there’s a real, tangible rule behind it now. So we must do that. And he understands that.”

The decision reverberated most in the ninth inning, when the Nationals put Rosenthal, one of the best closers in baseball, on the ropes. With the Nationals trailing 4-2, Zach Walters drew a one-out, pinch-hit walk. Denard Span reached after his line drive hit Rosenthal’s backside. Rosenthal balked, pushing the tying run into scoring position.

Up came the No. 2 spot in the Nationals’ lineup, the one now occupied by Frandsen, the gritty utility man the Nationals signed at the end of spring training. Frandsen swatted an RBI groundout to third base and left the game to Jayson Werth.

Werth took a pair of mighty hacks at two 99-mph, chest-high fastballs. Had he made contact, the result may have set back repairs on the Capitol dome. But he missed both, and the game ended.

“Take your shots,” Werth said. “I felt good about those swings. I bet he feels good about those pitches, too. What are you going to do? You take your shots. I got a chance to win the game right there. I felt like I took good swings. You tip your cap sometimes.”

After the Nationals retreated to the clubhouse, Harper’s teammates mostly steered clear of evaluating Williams’s decision.

“It has nothing to do with me,” Werth said. “I’ve played on teams where if you don’t hustle, you get taken out of games. Pretty standard. You talk about taking care of your area — that’s not my area. I think it’s part of the game. You show up here. You be on time. You hustle. Not a lot is asked of us. But we’re focusing on one, small part of the game, I feel like.”

“That’s up to Matt,” said starter Jordan Zimmermann (1-1), who allowed four runs — just one earned — over seven innings. “I don’t have much to say about that. I try to stay out it. Hopefully he learns, I guess.”

“Coach’s decision,” said Danny Espinosa, who drilled a homer for the Nationals’ first run.

Williams has made many decisions already, and he will make many more over the next five months. Few will be dissected like the one made Saturday afternoon.

More on the Nationals:

Nationals Journal: Strasburg sticks to his routine

Nationals Journal: Span returns from concussion