Nolan Arenado rounds the bases after his home run in the seventh inning put the Rockies ahead of the Nationals for good. (Matthew Stockman/Getty Images)

This game could have begun in the sixth inning — and it practically did — because starters and early offense don’t deliver results at Coors Field.

What does? Bullpens, late runs, whichever team can smack more balls through Denver’s thin air and to where fielders can no longer reach. That team, on Monday, was the Colorado Rockies in their 7-5 win over the visiting Washington Nationals. The Nationals, coming off an up-and-down weekend in Miami, separated themselves in the fourth, stumbled in the fifth and, in the seventh, saw a Nolan Arenado solo homer account for the winning run. They are now 1-7 in series openers this season.

“It’s a like a boxing match,” said Nationals second baseman Brian Dozier. “Every time you come here, putting up a few runs is never enough.”

Arenado, one of baseball’s best players, finished with three hits, two doubles, that home run, two RBI and three runs scored. Reliever Wander Suero gave up the seventh-inning blast and was tagged with his second loss of the season. Kyle Barraclough entered in the eighth and allowed a Raimel Tapia solo shot that gave Colorado a critical insurance run.

The Nationals fell to 10-11 with the loss, and are still searching for some semblance of consistency as April drags along and May nears. Their starter Monday, Jeremy Hellickson, lasted five innings and gave up five runs. Rockies starter Tyler Anderson also allowed five and was chased after three innings. Washington couldn’t use Anderson’s rough outing as a trampoline, like so many teams do once they jump ahead of the Rockies here. Instead their offense flatlined once Anderson exited the game.

“It’s just a matter of us putting good at-bats together,” said Washington catcher Yan Gomes. “I think we did, we were just kind of like one knock away from breaking the game open, just like they were.”

This was Hellickson’s first time pitching at Coors Field in his 10-year career, and it was the only park in which he had never appeared. That meant, until now, that the 32-year-old had avoided a clash of competing styles. Coors is as hitter-friendly as they come, with its deep dimensions, yawning gaps and high-altitude air that makes balls carry. Singles turn into extra-base hits. Long flyouts stretch to home runs. So starters such as Hellickson — soft-throwing, pitching to contact, nibbling on the edges with off-speed stuff — can get swallowed up fast by this stadium.

And he did on Monday.

The Nationals grabbed a two-run, first-inning lead on a Howie Kendrick single that scored Adam Eaton and Juan Soto. Kendrick made his second consecutive start at third base in place of Anthony Rendon, who is still recovering from a left elbow contusion suffered when he was hit by a pitch Saturday. Kendrick also, with that hit, gave Washington a slight margin for error before the temperature cooled and the offenses heated up.

But that advantage vanished just as quickly as it arrived. The Rockies erased it with a single from David Dahl, a double from Arenado and a single from Ryan McMahon that equaled two runs and a tie game by the start of the second. Dozier pushed the Nationals back ahead in the fourth with a towering three-run home run that nearly reached the concourse beyond the left field seats. It ripped through a cold night at 106 mph and landed some 435 feet from home plate. But it only built another lead that wouldn’t last.

Hellickson’s fifth and final inning was marked by three hits and three runs that evened the score. Trevor Story knocked in Arenado with a single. Then Mark Reynolds, who played 86 games for Washington last season, then lifted a Hellickson change-up over the center field wall. Reynolds’s soft swing led to a pop-up that floated and floated until it had floated out of sight. Call that the Coors effect.

“You get a three-run lead, it doesn’t matter who you’re facing or where you’re at, you can’t give up three runs there,” said Hellickson, gritting his teeth a bit. “It doesn’t matter where you’re playing.”

The Nationals, meanwhile, saw 13 of their hitters set down in a row following Dozier’s homer. They could not solve relievers Chad Bettis for three innings, or Seunghwan Oh in the seventh, or Scott Oberg in the eighth, or closer Wade Davis in the ninth. That helped the Rockies on Arenado’s homer, which was his 1,000th career hit and came on Suero’s second offering. It was a cutter from Suero, his best pitch and the reason Dave Martinez has begun to trust him in high-leverage situations. But it caught way too much of the plate — Martinez described it as “just right down the middle”— and Arenado didn’t miss it.

The deficit doubled an inning later once Tapia’s homer snuck inside the right field foul pole. The Nationals’ bats woke up again in the ninth, if only for a moment, when Ryan Zimmerman led off with a double. A Dozier walk followed to put the tying run on base with one out. But Kurt Suzuki soon grounded to Arenado, who fielded the chopper, stepped on third base and fired the ball across the diamond for a game-ending double play. There he was again.

Premier talent delivers results at Coors Field, too.

“Typical Colorado game,” Dozier said. “We just came up short.”