Trevor Rosenthal has a 40.50 ERA in seven appearances this season. (Nick Wass/Associated Press)

DENVER — It had been seven games since Trevor Rosenthal’s last appearance — 71 innings, to be exact — enough time for the Washington Nationals bullpen to appear, if only for short stretches, as a functional group.

Then Rosenthal entered in the eighth inning at Coors Field on Wednesday. Then the reliever had trouble controlling his pitches. Then the Nationals were reminded, once again, that Rosenthal’s struggles have been the biggest issue of their season. And they haven’t gone away.

“We got to see what he can do, and at this point he just doesn’t look right right now,” Manager Dave Martinez said after Rosenthal gave up three earned runs in a 9-5 loss. “We got to figure something out. I know we need him, but we have to figure out what’s going on and get him right.”

Rosenthal tucked a new round of concerns into a 31-pitch inning against the Rockies. He hit Charlie Blackmon with his second offering. He threw three wild pitches. He missed way low and way high and, in all, allowed three runs on a walk and two hits to let Colorado pull away. Afterward, after his seventh outing of the season had brought more of the same, Rosenthal echoed familiar words: He feels good. He feels frustrated. He feels like he is close, maybe just a game or two away, and just wants to get back out there as soon as possible.

But how much longer can Martinez call on Rosenthal, cross his fingers and watch innings unravel? When will enough really become enough?

“I got to really sit down and talk to him and see what’s going on,” Martinez said when asked whether he thought the problem was physical or psychological. “I’m not going to make any assumptions, and we’ll go from there. But we need him.”

Washington signed Rosenthal to a one-year, $7 million contract in late October. The idea behind the deal, loaded with performance incentives, was that Rosenthal would be the Nationals’ setup man. Maybe, the thinking went, he could even spell all-star closer Sean Doolittle for the occasional save opportunity. But it all hinged on how Rosenthal pitched following a year off recovering from Tommy John surgery. Spring training provided mixed results: a fastball that touched 100 mph, a spotty slider, command issues the Nationals passed off as preseason smoke. The start of the season was a nightmare.

It took the 29-year-old four appearances and 47 pitches just to record an out. By the time he did, against the Philadelphia Phillies on April 10, he had allowed seven earned runs. He tinkered with his mechanics, trying to stay lower in his delivery, and attributed some troubles to over-excitement. He finished that inning in Philadelphia to move his ERA from infinity to 72.00. He followed six days later with a one-inning outing against the San Francisco Giants, walking one and allowing a run but also striking out two on 27 pitches. It looked like he may be inching back to normal, one hold-your-breath pitch a time, then Wednesday devolved into another setback. He now has a 36.00 ERA and has faced 28 hitters over three innings. He has issued nine walks and allowed 12 runs, all earned.

“Looking at today’s outing, I’m trying to make a really good pitch and I’m having a bigger miss than I would like,” Rosenthal said in Denver. “So it’s making the smaller misses compound a little bit more. I feel good, and I feel like I’m really close. It’s just getting over that hump. I think it’ll happen soon. It’s just a matter of continuing to get in there and keep working.”

In theory, the only way for Rosenthal to fix this is with more opportunity. But the Nationals, at 11-12 and in a very competitive division, don’t have much room to experiment with a bullpen that has a league-worst 7.07 ERA. They also cannot choose to option Rosenthal to the minor leagues. Because of the seven-year veteran’s service time, he’d have to accept an assignment.

It’s a handcuffing situation for Martinez, who has been criticized for his bullpen management in the past. Rosenthal’s struggles leave his manager only six arms to choose from in high-leverage spots. It has caused him to use Doolittle in 11 of the first 23 games. Doolittle has a lengthy injury history, is looking to complete his first full season as a closer and has never made more than 70 appearances. Wander Suero, Justin Miller and Kyle Barraclough, swapped into the eighth inning in Rosenthal’s place, have been overtaxed, too. That’s the ripple effect of Martinez not knowing how or when to pitch Rosenthal or wondering whether he can at all.

Martinez is left to navigate what’s best for Rosenthal, what’s best for the Nationals and the wide gray area in between. Rosenthal acknowledged that more frequent outings could help him find a rhythm. But at the same time, he knows the results haven’t justified trust.

“It’s just hard because I’m not used to having that much time,” said Rosenthal, who was an all-star closer for the St. Louis Cardinals in 2015. “But if that’s going to be the case, I just need to find some extra time in between to put in some more work and have myself be ready.”

So the pitcher keeps hoping for another opportunity. And the team keeps hoping the next one clicks. Yet until Rosenthal can control his pitches, limit the walks, get stress-free outs, Washington’s bullpen will keep scrambling with him.

A team carries too few relievers for one to be unusable. A season is too short to force something that won’t work. Hope can’t be the only answer as April turns to May. Eventually, maybe soon, the Nationals’ front office will have to try something else.

“In the past, the issues have been fatigue or small injuries and trying to battle through things,” Rosenthal said. “But I think that’s the most frustrating part: I feel so good, and I want to try harder. But it’s almost like the harder I try, the more it hurts me.”

More on the Nationals:

Why Patrick Corbin and Yan Gomes became battery mates for the Nationals

‘We expected better’: Nationals close road trip with another series loss at Colorado

Max Scherzer expects to make his next scheduled start Friday

In a tight NL East race, the Marlins — yes, the Marlins — could decide the division