In early fall, when the sun sets low behind home plate in the late afternoon, Nationals Park’s outfield morphs into a treacherous place. Sunglasses and eye black are mandatory, but neither provide much relief. Routine flyballs can become the kind of hits that change an otherwise dandy Sunday, and maybe even slow down the home team’s plans to clinch a division.

The Washington Nationals’ 6-2 loss to the Milwaukee Brewers on Sunday afternoon turned on flyballs made noteworthy only because of the sun. In his first start in two months, Chien-Ming Wang pitched well for four innings but allowed at least one run because Bryce Harper lost a ball in the sun. In the seventh, the Brewers’ decisive three-run rally came together as Jayson Werth settled under a ball, and rather than catching it he ducked, blinded and defenseless.

“You can’t catch what you can’t see, you know?” Harper said. “Nothing you can do about it. The sun monster got me.”

Afterward, the Nationals ran a promotion in which players and coaches gave their uniforms to fans who had won a raffle. “It was a good day to give the jersey away,” Manager Davey Johnson said. “I don’t wanna wear that one. That one was unlucky.”

The Nationals’ list of positives ended at Wang’s strong showing in his first start since June 19 and Ian Desmond’s 2-for-2, two-walk day, which raised his batting average to .301. The team committed two errors, yielded four walks and allowed 15 hits. Bad news came from out of town, too.

The Atlanta Braves’ victory in Philadelphia sliced the Nationals’ lead in the National League East to 41 / 2 games, the lowest it has been since Aug. 28. After the Cincinnati Reds lost to the Los Angeles Dodgers on Sunday night, the Nationals retained the best record in the majors by half a game.

The Nationals’ magic number stayed at six with 10 games remaining, which means they can still clinch during their series this week against the Phillies at Citizens Bank Park.

The Nationals entered the seventh inning Sunday tied at 2, Ryan Matthues taking over after scoreless relief innings from Craig Stammen and Zach Duke. After an infield single and a fielder’s choice, Aramis Ramirez roped a double to right field, putting two men in scoring position with one out. Mattheus intentionally walked Corey Hart to load the bases.

Jonathan Lucroy rolled a grounder up the middle, and Desmond made a slick diving play behind second base. He tried to flip the ball with his glove to Danny Espinosa, but the ball dribbled away and the Brewers had taken a 3-2 lead.

“I tried to do everything I could,” Desmond said. “Just couldn’t get him out.”

Mattheus seemed to extricate himself from the jam when Carlos Gomez skied a flyball to shallow right-center field. Werth sprinted over, settled under the ball . . . and then turned his back. He couldn’t see it. One run scored. Jean Segura grounded out to Desmond, but rather than providing the third out, it only scored another run, putting the Nationals down three.

“I mean, he’s pretty good out there,” Johnson said. “He knows how to use the glove, block off the sun until the last minute and then snatch it. But, tough day.”

In the Nationals’ clubhouse after the game, Werth was not in the mood to talk. “You guys saw the game,” he said to a pack of reporters.

After the fly toward Werth plopped to the turf, Harper picked up the ball and threw it in, then turned to talk to Werth. “We just laughed,” he said. “There’s nothing you can do.”

Harper knew from experience. In the fourth inning, Ryan Braun led off with a flyball to shallow center field. Harper trotted forward, then slowed down trying to find the ball. He couldn’t, and it fell in as Braun scampered to second for a pop-up double.

“Once 4:05 comes around, you’ve got the shadows at the plate, you’ve got the left field stands with the red seats or whatever and then you’ve got the sun monster behind,” Harper said. “It’s just something that happens. You’ve just got to play with it, and hopefully it doesn’t happen anymore.”

The Nationals, though, play another day game Monday afternoon. Johnson said Nationals outfielders may begin taking practice in the afternoons before night games. Sunday, he positioned outfielders in order to minimize their exposure to the most troublesome sun spots.

“And then they started hitting the ball where we weren’t playing,” Johnson said. “Strategy, nothing worked today.”

The breaks spoiled Wang’s spot start, necessitated by the Nationals’ doubleheader Wednesday. Wang allowed two runs on eight hits in four innings, but he pitched better than his line indicated. Two of the Brewers’ hits off him did not escape the infield and another came on Harper’s misadventure with the sun. Wang walked none and threw 47 of his 69 pitches for strikes.

“It really means a lot and I’m really happy to pitch on the mound again here,” Wang said.

The difference in quality between his pitches Sunday compared to earlier in the year was striking. Wang’s sinker dive-bombed at 93 mph, dropping like a cannonball as it reached the plate. He sprinkled in a slider that moved sharply enough that Rickie Weeks swung at one for strike three. Of his 12 outs, 11 came either on groundballs, strikeouts or double plays.

“That’s probably the best we’ve seen him all year,” Desmond said. “He was good. A lot of hitters were saying he had a lot of late life on his ball.”

Wang allowed only one truly hard-hit ball, a double in the fourth by Logan Schafer off the base of the right field wall. The hit, which came three batters after the ball Harper lost, scored Corey Hart and gave the Brewers a 2-0 lead.

The Nationals tied the score in the fifth, scoring their first run on Chad Tracy’s pinch-hit single and another on Werth’s sacrifice fly deep to left. But they couldn’t beat either of their opponents, the Brewers or the monster shining overhead.

“What are you going to do?” Desmond said. “Tip your cap to the sun.”