WASHINGTON -- Physically, Pablo López feels right at home. The average velocity on his four-seam fastball on Saturday tied his last outing -- the first after a months-long stay on the injured list -- for the fourth highest of his career. The same fastball topped out at 96 mph -- something he had done only 16 times in his career entering the start.

But the mental side of things remains a problem without a clear solution, exemplified in Saturday’s 7-0 loss to the Nationals at Nationals Park. Lopez recorded a pair of career worsts: both his shortest outing (three innings) and the most homers he has allowed in a start (three).

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It led to Miami's 14th consecutive road loss, which capped a 7-22 August for the club.

“It’s being able to slow the game down,” Lopez said of his struggles. “The game speeds up on you very fast sometimes. Having that feeling, that mental cue, mental thing -- anything to get yourself back being in control, controlling what you can control and slowing the game down.”

The game sped up on Lopez on Saturday. And quickly. The Nationals blasted a pair of two-out back-to-back jacks in the first inning, and by the time Kurt Suzuki hit the Nats' third of the night two innings later, Marlins manager Don Mattingly decided there was no benefit to keeping the 23-year-old right-hander in much longer.

“Yeah, he wanted to go back out,” Mattingly said of Lopez, who was yanked after 63 pitches. “I just thought: Enough. We need to just start over with him.”

On paper, Lopez’s course of action on Saturday night had the ingredients of a steadying performance. Mattingly said he wants Lopez to challenge hitters because aggressiveness on the mound is what has gotten him to this point so far. But in the age of can’t-miss pitching, Lopez missed three times too many. And twice, he missed too far inside, hitting a pair of Nationals.

“I felt like my fastball was there,” Lopez said. “Some I didn’t execute as well, but I didn't have anything else working to back it up. And it’s hard when you don't have that against a lineup like the Washington Nationals. When you don't have anything other than your fastball and you’re not locating your fastball very well, you're going to run into some barrels like I did tonight.”

The speed of the fastball was not an issue. It was command, Lopez and Mattingly said, and the erratic location was not aided by a rough trial of pitch selection, which itself was not helped by a lack of usable pitches.

“For the most part, it didn’t feel like he had any secondary going to get a breaking ball over,” Mattingly said. “And that’s trouble with that club over there. You’re not getting some secondary over to slow them down a bit, you start getting in fastball mode. And I don't think anybody's quite good enough to get through them like that.”

Added Mattingly: “You do want him to be aggressive in the strike zone, but we also know that we have to be able to mix, too. And it seemed like today that wasn’t working very well.”

Lopez was already operating on Saturday night with little margin for error while opposing Nationals ace Stephen Strasburg. A night after what seemed like, for a moment, a magical comeback win, the offense was held to just two hits by Strasburg -- both in the first inning -- before he retired 22 in a row while racking up 14 strikeouts.

This came after the National League Cy Young Award candidate has won his last 12 outings against Miami.

“He seems like he’s always good with us,” Mattingly said of Strasburg. “I think there was a game in Miami I felt he was really, really good. This is probably right there with that.”