Matt Williams on benching Bryce Harper for "Lack of hustle."

Bryce Harper grounded back to the mound in the sixth inning of this afternoon's game and was slow getting out of the box when St. Louis Cardinals' starter Lance Lynn fielded the weak bouncer and threw to first for the out.

Harper turned toward the dugout 3/4s of the way down the first base line and jogged back to the Nationals' dugout.

Washington Nationals' Matt Williams apparently did not like what he saw on the play, because he benched Harper for lack of hustle, sending Kevin Frandsen out to left field to start the top of the seventh inning.

After the game, a 4-3 loss to the Cards, Williams explained his decision to reporters.

The reason he benched the 21-year-old, 2010 no.1 overall pick?

"The inability to run 90 ft.," Williams said succinctly.

Asked it was a case of the left quad issue Harper has been dealing with causing him to take it slow, Williams said, "No."

"Lack of hustle," the first-year skipper said. "That's why he came out of the game."

"We made an agreement," Williams continued. "He and I made an agreement. This team made an agreement. That when we play the game, we hustle at all times. That we play the game with intensity and the willingness to win and as it turned out, his spot came up, Kevin Frandsen put on a nice AB against [Cards' closer Trevor] Rosenthal, but his spot came up with the ability to win the game and that's a shame for his teammates."

• Here's the play in question:

Here's the groundout that led to #Nats' skipper Matt Williams benching Bryce Harper for lack of hustle. https://t.co/grkEhwLyia

— federalbaseball (@federalbaseball) April 19, 2014

The at bat Williams referred to came with runners on first and second with one out in what was then a 4-2 game. A balk with Frandsen at the plate moved both runners into scoring position and Frandsen's sac fly made it 4-3. Jayson Werth K'd swinging in the next at bat to end the game.

Harper's reaction to the benching?

"I'm not going to go there," Williams said. "You can ask him the question, but we made that agreement and you have to live up to it. Today he didn't."

Harper was asked for his reaction to the benching after the loss to the Cardinals.

Did he understand his manager's decision?

"Yeah, absolutely," Harper said. "I respect what he did, and it's part of the game."

Asked what Williams said, Harper told reporters, "Nothing. He just told me [Frandsen] was going to left. I said, 'Okay.'"

Being forced to watch his spot in the order come up with the game on the line was hard for him.

"That's tough to watch," Harper said. "Being able to be up there in that situation is something that I thrive on and I want to be in. It's just in the past and nothing we can do about it now."

Williams was clear, however, that it wasn't something he's seen before, or a pattern for Harper, it was just about the way they all agreed to play the game.

"It's just the way we set out to do it," he explained. "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," Williams continued, "he needs to play with aggression and the way he plays."

Will Harper play tomorrow?

"Oh, of course," Williams said. "He's going to be in the lineup tomorrow, but he made that agreement."

Cardinals 4-3 over Nationals in nation's capital

Photo © Joy R. Absalon/USA TODAY Sports

"He's an exciting player. People come and pay money to 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. And the other side is that 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."

Williams' thinking was simple, you can never assume anything.

"There's a million reasons why," Harper should have run through the base, he said. "The transfer rules that we've seen lately, what if that guy bobbles the ball as he's throwing it around... and he doesn't touch the base... He's out. He veers to the dugout, he's automatically out. Beyond all the, 'Just run 90 ft,' stuff, there's a real tangible rule behind it now, so we must do that. And he understands that."