Max Scherzer left the game with the score tied, but the bullpen allowed four runs to score in the eighth as the Nationals fell to the Rangers. (Mark Tenally/Associated Press)

All Max Scherzer could do while the Washington Nationals’ bullpen crumbled again Sunday evening was drop his head. He stood at the top step of the home team’s dugout at Nationals Park, his arms hanging over the railing, as Blake Treinen surprised Matt Wieters with a fastball that ricocheted off the crossed-up catcher’s wrist far enough away for Delino DeShields to sprint home and give the Texas Rangers the lead. Three pitches later, Elvis Andrus snuck a groundball down the left field line for a two-run triple and the knockout blow in the Rangers’ 5-1 victory.

Scherzer observed helplessly, his historic 10-strikeout performance in the sweltering heat wasted because Washington’s maligned relief corps, now without closer Koda Glover for at least 10 days, discovered a new way to fail for the second time in 24 hours.

“Everybody’s frustrated,” Scherzer said.

But it wasn’t the only glaring issue as the first-place Nationals (38-24) suffered their first three-game sweep and fell to 13-13 in day games. The offense mustered just six runs in the three losses, and Sunday’s run shortage was the most puzzling because it came against Austin Bibens-Dirkx, a 32-year-old career minor leaguer with one major league start before Sunday. The right-hander allowed one run over seven innings, plowing through Washington’s lineup with an assortment of junk.

By the eighth inning, Nationals catcher Matt Wieters was downcast. (Greg Fiume/Getty Images)

It initially appeared as if the Nationals were going to have their way with Bibens-Dirkx. Brian Goodwin, batting leadoff for the first time in the majors, began the first inning with a blast into the Nationals’ bullpen. Then Bryce Harper, batting second for the second time this season, hooked a single to right field.

But that was it for the Nationals until the seventh inning. Bibens-Dirkx, who spent some of 2012 pitching for the Nationals’ Class AA and AAA affiliates, retired the next 19 batters. His approach ran contrary to Scherzer’s: Rather than compiling strikeouts, he baited the Nationals with a constant dose of sliders, curveballs and change-ups, and the Nationals kept biting. They pulled most of them, and the result was usually weak contact. Bibens-Dirkx posted just two strikeouts during that stretch, but just six balls were hit out of the infield.

“His first-pitch strike efficiency was off the hook,” Nationals Manager Dusty Baker noted.

Scherzer was matching his counterpart and had another hopeless man on the ropes in the fourth: Nomar Mazara, one of the most dangerous batters on the Rangers (30-32). Mazara didn’t stand a chance of hitting the 1-2 pitch coming his way. It was a wicked slider, in on the hands, too far in to connect. He swung and missed for strike three, giving Scherzer his fifth strikeout of the game and the first out of the inning.

It was efficient and overwhelming — like so many of the strikeouts Scherzer has piled up in a career, one gradually sliding into Hall of Fame territory. But this one was different. This one was No. 2,000 — a nice, round number only 79 players in major league history had reached before Sunday and only two — Pedro Martinez and Randy Johnson — had reached faster than in Scherzer’s 1,784 innings.

A graphic to celebrate the milestone appeared on the video board, which elicited a rousing ovation from the thousands enduring the year’s first scorcher to watch one of the greatest pitchers of this generation at his best. Teammates joined in. Scherzer paused behind the mound and reluctantly tipped his cap. That was the extent of his acknowledgment. Future Hall of Famer Adrian Beltre was up next. There was more work to do.

Scherzer struck out 10 in 7 1/3 innings, including career strikeout No. 2,000. (Greg Fiume/Getty Images)

“I’m facing one of the best hitters of all time in Beltre,” Scherzer said. “So I’ve got to stay locked in. It was tough for me to even tip the fans the cap because I realize what a great hitter he is.”

The pause didn’t interrupt Scherzer’s flow. He got Beltre to ground out and was in complete control after surrendering a solo home run to Shin-Soo Choo, one of the few hitters with a substantial history of tremendous success against him, in the third inning. He retired 15 of the next 16 batters. He struck out the side in the fifth and added two more strikeouts to finish with 10. It was his fourth straight double-digit strikeout game, his seventh this season and the 56th of his career.

The Nationals needed all 10 of them because their offense was having trouble solving Bibens-Dirkx. They didn’t get their third hit until Anthony Rendon singled with two outs in the seventh inning. Adam Lind then walked, signaling that Washington was perhaps about to break through. Instead, Bibens-Dirkx got Wieters to roll a groundball over to the first baseman to conclude the inning and his outing.

“It seems like he had about six different versions of off-speed pitches,” Wieters said.

Meanwhile, Scherzer stuck around for the eighth but couldn’t finish it. After getting Joey Gallo to ground out, Scherzer induced another groundball from DeShields that took a bad hop on Rendon at third and resulted in an error. Two batters later, Scherzer issued his only walk to Jurickson Profar with his 109th pitch, which coaxed Manager Dusty Baker to pull him with one out and Choo due up next. Scherzer received a warm ovation for his 7⅓ innings, which temporarily masked the anxiety that arises when the baton is passed to the Nationals’ bullpen.

“He gave us all he had,” Baker said.

That anxiety quickly surfaced, though, because Oliver Perez walked Choo on four pitches to load the bases. Baker then called on Treinen, a groundball specialist, to escape disaster with a double play. But he could not, and all Scherzer could do was drop his head.

“It was a bad weekend,” Baker said.