Nationals rookie left fielder Juan Soto high-fives teammates after Sunday’s 6-4 win over the Braves. (Adam Hagy/USA Today Sports)

On afternoons like this, when the Washington Nationals took an early lead on the first-place Atlanta Braves and added to it late, one could easily mistake them for a perennial division leader cruising to another title.

Because when Bryce Harper and Anthony Rendon homer, when Tanner Roark pitches like he is capable of pitching, this team resembles the playoff contender many expected it to be. But as the Nationals finished their season series against the Braves with a 6-4 victory Sunday, what might have been lingered like it has so often lately. They finished 9-10 against the Braves and have won seven of their past nine games.

“I feel like we should’ve been doing this all year,” Rendon said. “So that’s maybe what we could take from it.”

Harper hit his 34th home run, a two-run shot off tough Braves left-hander Sean Newcomb. Those two RBI moved Harper to 97. Never in his decorated career has he driven in 100.

Current widespread front-office thinking holds that RBI do not say much about a player’s productivity, but the statistic still means something to players — and should illustrate how completely Harper has turned his season around since struggling in the first half.

Harper entered Sunday with a .305 batting average and .985 on-base-plus-slugging percentage since the all-star break, 11th best among qualified major leaguers. Most of the 10 players ahead of him have legitimate MVP cases.

Like so many things this season, Harper’s surge was too little and too late to save the Nationals, but not too late to save his first year before free agency. Entering Sunday, his OPS was just a dozen points lower than his career norm — far lower than in his MVP season but not unheard of. His .249 average is far lower, but he began Sunday with the fifth-best on-base percentage in the National League, which increased when he reached four times (a homer, a hit and two walks, adding to his league-leading total).

“It’s a bummer when we’re not winning ballgames. That was the biggest thing on my mind,” Harper said. “I’m not really worried about my numbers or anything like that because I am who I am. That sounds bad, but I am. Any given [game], I’m able to go out there and do some things for this team that are special, and I was able to do that again today.”

The man who has been hitting behind him regularly, Rendon, is also having another strong offensive year — though once again, no one seems to notice. He hit his 20th homer Sunday, a two-run shot that moved him to 75 RBI in a season in which he missed three weeks with a broken toe. He also singled twice and drew a walk, and his batting average is .300.

Should Harper depart in free agency, the Nationals (76-74) could reallocate the funds they would have used to sign him to signing Rendon long term, a deal that would likely cost far less and perhaps secure as much productivity. Since 2016, Rendon has accumulated 15.8 wins above replacement by the FanGraphs calculation, 11th most in baseball. Harper’s WAR in that span is 10.9 — behind 34 other players.

“He’s just really good,” Manager Dave Martinez said of Rendon. “He understands the game, and he understands himself as a hitter.”

That Harper recovered and Rendon continued his production inspires a question that has puzzled many around this team. How — if two of their key players are as productive as ever and they welcomed the emergence of a new star in rookie Juan Soto, who drove in their sixth run with a ninth-inning single Sunday — are the Nationals just two games above .500? How did the Braves (83-66) end up a combination of six wins and Nationals losses away from eliminating them from playoff contention?

Part of the answer lies in the Nationals’ starting pitching, which has not made as many leads stand up as it normally would. Roark, who threw 5⅓ innings and allowed two runs Sunday, owns a 4.34 ERA. His career mark is 3.58. His struggles and those of other teammates, plus the loss of Stephen Strasburg for two months, undermined the pitching staff. The 2017 Nationals rotation pitched to a 3.63 ERA, top five in the majors. After Roark’s start Sunday, Nationals starters have a 4.06 ERA this season, 15th in the majors and fourth out of five teams in the NL East.

Those 5⅓ innings were enough from Roark, in large part because when he left in trouble, the bullpen bailed him out. Greg Holland surrendered a two-run homer to Charlie Culberson in the eighth, one of his first major lapses since joining the Nationals. But Sean Doolittle worked a scoreless ninth for his 24th save.

Save for a small part of this season, in the wake of all the trades, this bullpen has largely been stable. That the bullpen was not the problem for most of this season, after years of creating angst, makes this team’s failures even more maddening.

The 2017, 95-win Nationals bullpen finished with a 4.41 ERA. In 2018, the bullpen is pitching to a 3.90 ERA.

Many of the numbers simply do not add up, too good for a record this mediocre, too impressive for a season so disappointing. This team has been less than the sum of its parts, which is why its series win over the Braves only delayed the near inevitable, and why this team is now playing for a winning season instead of a championship.