Each baseball season naturally divides into chapters of sorts, months or weeks, homestands or road trips, each characterized by one particular source of adversity or another. In the course of six months of baseball, segments become a method of survival: Get through this road trip, get to that day off, then move to the next. The big picture is so big that it is often best to pixelate.

These Washington Nationals, comfortably ahead in their division, uncomfortably strained by their schedule, find themselves at the end of one such stretch, embarking on another. After Monday night’s 4-0 win over the Philadelphia Phillies, they are 18 games into a stretch of 20 games in 20 days, nearing the end. They are also 1-0 in a stretch of 22 straight games against National League East competition, another potentially pivotal span.

The Nationals have the best record against their division of any team in baseball, just ahead of the Chicago Cubs. They built it largely on the back of pitching performances like the one Tanner Roark turned in Monday night — seven scoreless innings on exactly 100 pitches.

The outing dropped Roark’s ERA to 2.87, lowest of any of the Nationals’ starters. He pitched at least seven scoreless innings for the eighth time this season, most in the majors. Roark ranks in the top 10 in baseball in ERA and innings pitched. A season after he was bumped to the bullpen, he has made an argument for the title of most consistent Nationals starter — an honor in any rotation, a powerful endorsement in this one, though it often seems the rest of baseball has not noticed him much at all.

“It would be fine if they didn’t take notice, and then he can surprise them,” Nationals Manager Dusty Baker said. “But soon here, he’s not going to be surprising anybody because everybody knows what he’s done. Everybody has stats. Everybody has video. We just want more of the same.”

Jayson Werth celebrates with second baseman Daniel Murphy after hitting a home run during the first inning. (Eric Hartline/Usa Today Sports)

[Michael A. Taylor is recalled, Lucas Giolito sent back to Class AAA]

Roark’s Monday night cruise through the Phillies’ lineup also took pressure off the Nationals’ bullpen, which got a bit of a break Sunday but can always use more. With Joe Ross on the disabled list for the entire 20-games-in-20-days stretch and Stephen Strasburg on the disabled list for most of it, the Nationals’ rotation has sputtered: Second in the league in starters’ ERA for most of the season, Nationals starters entered Monday with the 16th-best ERA in the majors in August, 4.51. They began the day 15th in August in innings pitched.

All of that, of course, strained the bullpen, the inspiration for a great deal of August angst. The Nationals used three relievers Sunday and two — Marc Rzepczynski and Mark Melancon — Monday, meaning Roark’s performance also helped breathe life into a bullpen that will be resuscitated further by Thursday’s day off and the expansion of rosters after Sept. 1.

“August is a grinder month,” said Roark, who said he has learned the key to staying strong is sticking with his day-after workouts and not giving himself a break. “It’s when everybody’s got to stay checked in. You’ve got to keep playing as a team, keep going hard. There’s bumps and bruises here and there, and stuff like that, but you’ve got to keep going.”

[Nationals plan to add Mat Latos in September]

One might expect stretches like these, which include no days off and endless heat and humidity, to take a particular toll on more experienced everyday players — like Jayson Werth, who is in his 14th season. But instead of fatigue, he has displayed power.

Phillies fans will probably never stop booing Werth at Citizens Bank Park, an unorthodox greeting for a World Series hero, though customs do vary. Monday, he responded with a first-inning home run, his 19th of the season and sixth in Philadelphia in the last two seasons. It was his seventh home run of August, tied for the most he has hit in a single month since leaving the Phillies in 2010. August, like that 20-games-in-20-days stretch, is not over yet.

Mark Melancon and Wilson Ramos celebrate the series-opening win in Philadelphia. The 20-games-in-20-days stretch is almost complete. (Drew Hallowell/Getty Images)

“I’ve just kind of always been that second-half type of player where the weather warms up and the season goes on and I find my groove,” Werth said. “. . . I don’t think there’s any rhyme or reason to it, it’s just how it is.”

Against Phillies rookie right-hander Jake Thompson, the Nationals added another run in the first when Bryce Harper walked and Anthony Rendon singled into the gap to score him. Roark had a two-run lead. But Thompson settled down, and the Nationals could not disrupt him, failing to put a runner in scoring position for six innings after that first-inning rally. They scored again in the ninth when Clint Robinson and Trea Turner each singled home runs. Turner’s hit extended his on-base streak to 19 games, during which time his seemingly effortless energy has lifted pressure to produce off more worn-down teammates.

[Bryce Harper’s a ‘diva,’ and Tom Boswell is cool with that]

Baker thinks of the season in months and said from the start that if the Nationals could win 15 games in each of them, they would be just fine. Monday’s win was their 15th in August. They have not won more than 16 in a month this season. If the Nationals finish this stretch strong, it could still be their winningest — if also their most grueling — month-long chapter yet. How have they handled it?

“I’ll let you know September 2,” said Baker, whose Nationals will be, by that time, well into their latest chapter, three weeks of games against the teams they handle best.