PITTSBURGH -- Washington rookie right-hander Joan Adon has the stuff to pitch in Major League Baseball, which is why the 23-year-old has been given an opportunity to hold down a spot in the Nationals’ starting rotation.

Through two starts, though, Adon has struggled to turn that stuff into results. He gave up six runs on nine hits and three walks in 4 2/3 innings Thursday night as the Nationals lost to the Pirates, 9-4, in the opener of a four-game series at PNC Park.

In Adon's first outing against the Mets on Saturday, he gave up four runs on four hits and four walks in 4 1/3 innings, and his early-season ERA stands at 10.00. 

But Nationals skipper Dave Martinez said the problems are not a lack of talent.

“It’s going to be a learning process with him,” Martinez said of Adon, who is ranked by MLB Pipeline as the Nationals' No. 8 prospect. “His stuff is good.”

A big part of that learning curve will be how Adon makes best use of his breaking pitch in the Majors. On Thursday, he had a difficult time locating it in the strike zone and got behind in some counts. That led to the three free passes and Pittsburgh batters jumping on his fastball.

“I was missing the zone with my breaking pitches, and I had to attack the zone with the fastball,” Adon said. “They were expecting it, seeing what was going on, and they took advantage of it.”

Martinez believes that earlier in his career, Adon would have gotten away with those misses, because lesser hitters might have chased them outside the zone anyway.

“He would get away with that,” Martinez said. “The biggest thing here is that when you get to this level, the chases go away a lot. You’ll get chases here and there, but when you’re missing your spots, big league hitters don’t chase. You’ve got to throw strikes. You’ve got to be around the strike zone.”

Adon is capable of throwing strikes. Walks have not been a major problem for him through the Minor League levels, and he does not think he has an issue with his mechanics.

“I feel like it’s more mental,” Adon said. “I’m trying to be a little too perfect with that pitch, and that’s why it’s missing.”

The other issue Martinez identified is a propensity to let big innings get away from him. Pittsburgh All-Star Bryan Reynolds hit a two-run home run with no outs in the third to tie the game, but instead of limiting the damage at that point, Adon let things snowball.

Yoshi Tsutsugo singled, Ben Gamel singled, Kevin Newman doubled and Washington never got the lead back after having jumped out to a 3-0 advantage in the first.

“It’s just that one inning that we’ve got to get him through,” Martinez said. “That’s something I talked about before with him. Just, ‘I’ve got to slow things down. I can’t speed things up. I’ve got to make sure I throw the balls where I need to throw them.’”

“It’s on me,” Adon said. “I have to control that. If I feel like the game speeds up on me out there, then it’s up to me to slow it down.”

Washington's bullpen couldn’t come to Adon’s rescue. Hunter Harvey allowed an RBI single immediately after replacing Adon with two outs in the fifth. Pittsburgh then scored another run in the sixth off Andres Machado and two in the seventh off Patrick Murphy. As a team, the Nationals walked eight batters.

“These guys got to come in and throw strikes,” Martinez said. "We’re down a couple runs -- if they shut the door down, it could be a different ballgame.”

The sloppy pitching performance wasted Washington's hot start, when Keibert Ruiz and Yadiel Hernandez hit back-to-back RBI singles with the bases loaded off Pittsburgh starter JT Brubaker in that three-run first inning.

But Brubaker and Pittsburgh's bullpen were able to make the adjustments that the Nationals could not.

“Their pitchers did a great job of adjusting to us and finished the game very well,” Ruiz said.