A.J. Cole allowed one run in 5⅔ innings as the Nationals beat the Phillies, 3-1. (Matt Slocum/AP)

There was faint applause from behind the visitors' dugout as A.J. Cole strode off the mound at Citizens Bank Park during the sixth inning of the Washington Nationals' 3-1 win over the Philadelphia Phillies on Monday. On a night when Nationals fans arrived in enemy terrain expecting to witness the stirring return of Bryce Harper, Washington's former MVP and the final piece to its playoff puzzle, they were expressing their appreciation for the latest solid performance from a spare part the Nationals envision helping next year, not next month.

There was nothing spectacular about Cole's outing on this unseasonably warm late September night. He threw 101 pitches over 5⅔ innings. He struck out five and walked two. He allowed six hits. His most memorable moment came when he notched a single to center field for his first career hit in the second inning, in his 24th career plate appearance.

"I've been waiting for that," he said.

But, most importantly, Cole allowed just one run on an Odubel Herrera homer and departed with a 2-1 lead, continuing his recent under-the-radar, sturdy but not spectacular stretch in a Nationals uniform.

Over his past seven appearances, bouncing uncomfortably between starter and reliever, the right-hander has a 3.36 ERA across 32⅓ innings. Erase a rough relief outing earlier this month, when he allowed three runs in two innings, and the ERA drops to 2.69.

Two seasons removed from a horrid major league debut in which he allowed nine runs in two innings, the 25-year-old Cole, whose luster has worn off since he moved through the ranks as a top-tier prospect, has provided the results to convince Nationals officials he could fill the fifth spot in their rotation next season at least until Joe Ross, who underwent Tommy John surgery in July, returns a few months into the campaign.

"He's commanding the strike zone," Nationals Manager Dusty Baker said. "He's kept it out of the middle of the plate. The one ball that was hit out was in the middle of the plate. So, if you stay out of the middle of the plate, you got action."

Cole's performance Monday allowed the Nationals (95-61) to overcome another mediocre offensive showing without Harper — though Daniel Murphy and Anthony Rendon also didn't play because they were given the night off. Baker said Murphy was dealing with "general soreness" while Rendon had a sore foot.

The Nationals left New York on Sunday in elaborate "Game of Thrones" attire — Harper included — expecting Harper to return to the lineup Monday after he missed 40 games with a bone bruise and strained calf in his left leg. But Harper didn't play because, Baker said, he woke up experiencing flu-like symptoms. He wasn't activated from the disabled list, and the Nationals had to go at least another day without him. After Monday's game, Baker said there's "a possibility" Harper could return Tuesday.

"We just have to see how he feels [Tuesday]," Baker said. "Because you hate to waste these days but, also at the same time, you hate to push him out there when he's not ready. Hopefully it was just an overnight thing, and he'll hopefully be ready [Tuesday]."

The Nationals could have used even a rusty version of Harper on Monday as they continued to struggle to scrape together runs without him in the lineup. In the 113 games before Harper's injury, Washington averaged 5.41 runs. Entering Monday, that number was 4.22 in his absence, and it dropped further opposite Philadelphia right-hander Aaron Nola, who allowed two runs and struck out nine across six innings to lower his ERA to 3.54 for the 62-95 Phillies.

But the Nationals mustered just enough support for Cole. With Harper out, Jayson Werth got the start in right field.

Batting fifth, Werth, who entered 2 for 30 over his past seven games, singled and scored on Michael A. Taylor's two-run homer — his 17th of the season — in the second inning.

In the eighth, after Ryan Zimmerman lined a double and rookie Victor Robles continued his convincing audition for a playoff roster spot with a line-drive single, Werth plated Zimmerman by beating out a potential inning-ending double play to give Washington a 3-1 edge.

The lead stuck because the bullpen pieced together 3⅓ scoreless innings, beginning with Oliver Perez, who relieved Cole with a runner on second base in the sixth. The left-hander walked the first batter he faced before getting pinch hitter Tommy Joseph, a right-handed hitter, to pop out to catcher Matt Wieters in foul territory to end the inning.

"You can look at turning points of the game, and that was certainly one of them," Baker said. "They had the top of the lineup coming up and Tommy Joseph can hit the ball out of the ballpark. So Ollie came in and did his job."

Matt Grace, Matt Albers and Sean Doolittle followed and each logged a perfect frame, and the Nationals matched their win total from last season with six games remaining, five victories shy of 100 and a franchise record.