Jacob Turner left with a one-run lead after six innings, but the Nationals could not make it stand up in a loss to the Rockies. (David Zalubowski/Associated Press)

A mile-high malady plagues visiting pitching staffs in Denver — the Coors Field Cold or something like that. After more than two decades of baseball here, somebody probably has come up with a better name for the condition.

Dusty Baker knows the virus well, from managing a Rockies’ division rival in San Francisco, making annual trips with the Reds, then watching a Colorado series decimate his bullpen last season. In his mind, months like this one are divided into two decisive periods: the week before Colorado, in which a bullpen must somehow avoid extra work, and the week after, in which it almost certainly will suffer its effects.

In Monday’s 8-4 loss to the first-place Colorado Rockies, the Washington Nationals’ pitching staff experienced an incubation period of approximately six innings before succumbing, and the bullpen again suffered most.

Jacob Turner’s impressive start jerked to a conclusion when Mark Reynolds hit a two-run homer in the sixth. Then Enny Romero surrendered a one-run lead when Charlie Blackmon hit a two-run shot in the seventh. Blake Treinen allowed five straight hits to open the eighth and left without recording an out in the inning.

“Those guys, we realize they’re tough here,” Baker said. “We just have to make a little bit better pitches. They weren’t bad.”

Turner was not particularly upset about the pitch Reynolds hit to cut a three-run lead to one. He was trying to be aggressive, he said later, and Reynolds beat him.

Romero was not particularly upset about the pitch Blackmon hit out to right field, high into the second deck, a shot that probably would have made its way out through the thickest of smog, let alone thin air. He wanted to throw a fastball, and Blackmon simply hit it, Romero said later.

“Sometimes, the hitters get paid just like our guys get paid,” Baker said. “And every pitch isn’t always a bad pitch.”

To the extent that a pitcher can allow five hits without being hit hard, Treinen did that, victimized by a few groundballs through the infield and a bloop to short left.

“Colorado’s a funny place,” said Adam Eaton, who played right field with Bryce Harper getting a day off. “. . . You play so deep so sometimes you give up the balls in front. As soon as you start moving in, they hit it over your head.”

Late-game chaos like that is a symptom of life at Coors Field. Balls will fly and leads will fly away with them, making the whole thing an experience to be survived since it cannot be avoided.

Yet if even healthy bullpens get the sniffles here, the Nationals could find themselves at risk for a full-blown flu. As they compiled their seven-game winning streak last week, the bullpen was not immune to misadventure. After Monday’s loss, Nationals’ relievers have compiled a 5.54 ERA and allowed 78 base runners in 52 innings.

The Nationals need Romero in spots such as Monday’s seventh inning because Sammy Solis is on the disabled list. Romero, who said he recently changed his delivery to command the strike zone better, is now pitching to 7.04 ERA in 7⅔ innings despite a strong weekend in New York.

Baseball logic holds that a sinker like Treinen’s should withstand the thin air of Coors Field, that groundballs will win here. Monday, they did not; five hits sneaked up the middle or through the left side. Treinen has allowed 22 base runners in 7⅓ innings of work.

Their struggles erased a strong start from Turner, who had the unenviable task of filling in for Stephen Strasburg while the ace was on paternity leave — and making his season debut at Coors Field. The Nationals chose Turner in part because he has pitched in the majors before, so a younger prospect would not have to make his big league debut in a place like this.

He gave the Nationals exactly what they had hoped for — six strong innings in which he allowed three runs. He did not walk a batter. If the thin air affected him, he exhibited no symptoms. Were it not for Reynolds’s home run swing in the sixth, Turner’s evening would have qualified as outstanding.

“He gave us all he had,” said Baker, whose team rallied against Rockies starter Tyler Anderson — the first left-handed starter they had seen all season — in the sixth.

Trea Turner’s double, Eaton’s triple, Anthony Rendon’s single and Ryan Zimmerman’s homer gave the Nationals a three-run lead in that inning. Then Jacob Turner surrendered a triple to Nolan Arenado and the home run to Reynolds in that inning. His chance at a win disintegrated an inning later.

“I was just trying to stay aggressive I think, especially here,” Turner said. “You can’t put extra guys on base if you don’t have to. So just trying to stay as aggressive as I can in the zone.”

The most important part of Turner’s outing was not the outcome but the length. While Baker said he hoped Turner would last through the seventh, the fact that he pitched through the sixth meant the Nationals’ bullpen needed to account for just two innings.

While those innings proved problematic, they did not drain the Nationals’ of their relief corps. Shawn Kelley, Koda Glover, Joe Blanton and Oliver Perez should be fresh Tuesday. No one worked more than an inning. With three more games in Colorado on the way, along with the threat of rain and delays and other April obstacles, the Nationals’ relievers will need their rest. The Nationals will not withstand the Coors Field Cold — or a four-game series with the winningest team in the National League — without them.