Starter John Lannan received little help Saturday from his defense, which committed three errors that led to seven unearned runs in Philadelphia. (Hunter Martin/Getty Images)

The Philadelphia Phillies need no help in beating anyone, but on Saturday night the Washington Nationals gave it to them, anyway. The Nationals struck down the scorching Phillies on Friday, and they behaved Saturday night as if they wanted to prove they could do it with a high degree of difficulty.

In an 11-3 loss at Citizens Bank Park, the Nationals set a new standard for making mistakes at the wrong times. Three errors led to seven unearned runs, the most the Nationals have allowed since baseball returned to Washington. Starter John Lannan’s defense let him down, but he could not be fully absolved. He yielded four unintentional walks in three innings, two to opposing starter Roy Oswalt, including the free pass that preceded the game spiraling out of control.

“You can’t give them extra outs, or they’ll capitalize,” Manager Davey Johnson said. “That’s what they did tonight. You can’t do that against a good ballclub.”

The Nationals followed one of the most encouraging days of their season — which included Bryce Harper’s walk-off home run for Class AA Harrisburg, Stephen Strasburg’s dazzling rehab start for Class A Potomac and a win over their divisional bully — with one of their dreariest.

Lannan took the mound with an odd mix of history swirling around. In his last start against the Phillies, on June 1, he finally broke the hex they held over him, winning against them for the first time in his 14th try.

He came back to the site of his major league debut. On that day, he hit Chase Utley and Ryan Howard in back-to-back at-bats, and home plate umpire Hunter Wendelstedt ejected him. The home plate umpire Saturday night? Wendelstedt.

The Nationals set a tone with the first batter of the game. Jimmy Rollins grounded to second base, and Danny Espinosa could not corral an in-between hop with his backhand. When Lannan retired the next two hitters, he still had to face Howard with one on. Howard drilled a sinker the other way. It traveled only 354 feet, but it snuck over the left field fence to give the Phillies a 2-0 lead.

“You’ve got to make pitches, no matter what happens out there,” Lannan said. “They make great plays for you. It’s my job to make pitches, and I didn’t, bottom line.”

The Nationals scored two in the second on an RBI double by Laynce Nix and a single by Ian Desmond. The score remained tied only briefly.

Lannan’s start came undone in the third with the aid of another error. Shane Victorino led off with a slow grounder to short. Desmond charged the ball and made a quick sidearm throw to first that sailed high, forcing Michael Morse to leap off the base.

“You can’t make mistakes against any team in the big leagues and expect to win,” third baseman Ryan Zimmerman said. “It’s just things we have to clean up, and we know that. It happens every now and then.”

Consecutive singles gave the Phillies the lead again before a walk to Hunter Pence loaded the bases. Here, in the midst of Lannan’s freefall, came one preposterously tremendous play. With the bases loaded and one out, Wilson Valdez chopped a swinging bunt between the mound and the third base line. Lannan bolted off the mound as the ball spun away from him.

Howard chugged down the third base line. As Lannan started to dive, the ball took a funny hop, causing him to stumble as he lunged. He scooping the ball with his glove and, in one fluid motion, while still in the air, Lannan flicked the ball toward home plate.

This was no ordinary glove flick. It traveled inches over Howard’s left shoulder and settled in Wilson Ramos’s catcher’s mitt. Howard had slowed just a bit, and he seemed confused when Wendelstedt called him out.

“I don’t think he knows how he did it,” Zimmerman said. “I think everyone was pretty surprised.”

Lannan may have been hurt on the play. His spike appeared to catch in the grass as he dove, and afterward, pitching coach Steve McCatty visited him on the mound. Lannan shook his head and insisted he remain in the game.

“I think I may have aggravated the patella tendon a little bit, but I mean, it’s fine,” Lannan said. “I’m not going to use the play as an excuse. The knee felt a little uncomfortable. It was hard to push off for a little bit, but I still have to make pitches.”

The highlight play could not stop the inning from unraveling. The bases were still loaded with two outs, and Lannan had a chance to escape with the Nationals down only 4-2. Then, for the second time in two innings, he walked the opposing pitcher. Oswalt’s free pass pushed home Pence.

“That,” Johnson said, “was the bonecrusher.”

Lannan seethed on the mound. He induced a bouncer to the left side by Rollins. Desmond ranged far to his right, made a backhanded stop and fired to Espinosa covering second, a slick play, but not in time. Espinosa stretched and lost balance. When he toppled over, Valdez scooted home all the way from second, scoring after Ramos could not handle Espinosa’s one-hop throw home.

The Phillies led 7-2, and they finalized their scoring with the help of one more error, a one-out grounder Morse booted at first base. The Nationals have vastly improved their defense from last season, but Saturday night reinforced the obvious: They might beat the Phillies if they play their best. They will definitely lose if they don’t.

That lesson learned again, they had only one thing left to do. “Turn the page,” Lannan said. “Turn the page and get over it.”

Nationals note: Morse showed no ill effects at the plate as he returned after missing one day with an elbow contusion. He went 2 for 4 with a double, a run and an RBI.