Tanner Roark catches up to Anthony Rendon as the Nationals celebrate their 10th consecutive victory on Thursday. The winning run scored on a throwing error after Rendon’s single in the ninth. (Jonathan Newton/The Washington Post)

Late Thursday afternoon, Anthony Rendon stood at his locker inside the Washington Nationals’ clubhouse and eschewed joy for measured caution. He had just given the Nationals their 10th consecutive victory with a game-ending base hit, one of five such “walk-off” wins during the thrilling streak. Rather than revel in the moment, Rendon reminded those within earshot of the coming fall.

“We’re just riding it as long as we can,” he said. “It’s a roller coaster. They always go back down. It’s baseball.”

Rendon’s words became prophetic the next night, when the Nationals’ streak ended with a loss to the San Francisco Giants. The Nationals observed the defeat in the same manner they had celebrated all the wins: with an eye of the next day, the next game. For them, what’s next is always more important than what has happened.

The Nationals’ winning streak tied the club’s longest since it relocated to Washington in 2005 and allowed them to reclaim and solidify their status as one of the favorites to win the World Series. The team will enter the stretch run of the regular season with a healthy lead in the National League East division, steeled by the triumphs and trials of the past two seasons.

They rose suddenly with a 98-win romp to win the NL East title in 2012, only to lose a heart-wrenching decisive playoff game. They fell just as suddenly in 2013, crumbling under expectations before a too-late surge in the season’s final month. Through it all, they have grown up together and emerged as a better version of themselves, among the best teams in baseball and eyeing a return trip to the playoffs.

“There’s a lot of guys in here that have played a lot of games and developed,” shortstop Ian Desmond said. “Fortunately for us, we’ve been able to maintain the same group of guys. I think, absolutely, everything has helped us — the wins, the losses, the ups and downs. I definitely think we’re stronger this year than we were last year and before 2012. This is the best Nationals we’ve been.”

After the Nationals beat the Giants, 6-2, in front of 34,137 at Nationals Park, they ended Saturday afternoon with a record of 74-54, best in the NL and in first place by 6 ½ games. The best simple indicator of a team’s future success is overall run differential — the number of total runs it has scored compared with its opponents. The Nationals have outscored opponents this year by 99 runs, best in the National League by a whopping 45 and tied for third in the major leagues.

“We’ve been playing pretty dang good ball all year,” left fielder Bryce Harper said. “We’ve had a lot of injuries. To be able to overcome those to get in the position that we are is pretty unbelievable. We’ve had a lot of help from our bullpen, a lot of help from our starting [rotation]. I think we’re right where we need to be.”

As the Nationals have risen, they have maintained a narrow focus on the present. The past two seasons have conditioned them to stay calm in the face of expectation, elation, disappointment or even a 10-game winning streak. After the 10th straight victory, Manager Matt Williams sternly said he would “refuse” to become caught up in excitement.

“It’s definitely more fun to win. I don’t want to say we were coming in [to the clubhouse] flipping our shoes off and going home,” Desmond said. “At the same time, we understood there’s still a lot of work, a lot of games left to be played.”

The businesslike attitude has grown from the Nationals’ past two seasons, a team-wide coming-of-age.

“It’s one more year of experience from ’12, when we were kind of new at winning, and ’13, where we built off that later on in the season,” General Manager Mike Rizzo said. “It gives us another year of experience. I hope we’re better for it. I hope we’ve learned. You learn from your successes and your failures, and you learn how to handle both things better. It really keeps you on an even keel.”

The Nationals needed the steadiness to play through a confluence of injuries. Harper, catcher Wilson Ramos, third baseman Ryan Zimmerman, center fielder Denard Span, first baseman Adam LaRoche and starting pitchers Gio Gonzalez and Doug Fister all missed games while on the disabled list in the first half of the season.

“I think we appreciate where we’re at, and it lets us know we need to make sure that we work even harder to get to where we want to get to,” Williams said. “Over the course of the season, it’s a little gratifying given where we came from and given what’s happened over the course of these last four months and the things that didn’t go right for us from a health perspective and anything else.”

The Nationals are still playing through another injury to Zimmerman, the franchise’s first draft pick after baseball returned in 2005 and still one of their best hitters. Zimmerman could return from a hamstring tear in mid-to-late September. Rizzo blunted the effect of Zimmerman’s absence by trading for veteran infielder Asdrubal Cabrera from the Cleveland Indians. Cabrera, who hit a home run in Saturday’s win, has provided dazzling defense at second base and the Nationals have won 14 of his 19 games.

“It’s really fun when you play with the guys like we’ve got in here,” Cabrera said.

In 2013, the Nationals allowed injuries and underachievement to derail a season that they entered as the consensus favorite. They have drawn motivation this season from that discontent.

“I think last year we got so caught up in winning the East [in 2012] — it was so great, blah, blah, blah, first time ever winning,” Harper said. “We came into that second year still locked in on winning the East that year. Last year didn’t go the way we wanted it to. Having the streak we did at the end of the season, almost getting back to the postseason, that’s tough. You have that terrible taste in your mouth.”

If the Nationals go back this season, they will have an entirely different outlook. When the Nationals played the St. Louis Cardinals in the 2012 NL Division Series, four of their 25 players carried postseason experience. On this season’s prospective postseason roster, as many as 21 players will have appeared previously in the playoffs.

The Nationals’ recent winning streak put them in prime position to return. Baseball’s roller coaster still has five weeks in store before the postseason. They plan to remain focused on only one goal.

“It doesn’t matter how many you win,” Desmond said. “If you win the World Series, nobody cares what happened along the way. You can’t tell me one statistic, but they’re world champions. They got the rings. It doesn’t matter how many games. None of that stuff matters. All you got to do is get there and play your best. You either win or lose. I don’t think any team comes into spring training and says, ‘Let’s win 100 games.’ They say, ‘Let’s win the World Series.’ That’s all that matters.”