Lucas Giolito. (Photo by Katherine Frey/The Washington Post)

VIERA, Fla. — Entering his first major league spring training, Lucas Giolito thought he would be among the first cuts because of his inexperience. The organization’s top prospect has made only eight starts above Class A. At 21, the right-handed starter was the youngest player in camp. But the Nationals kept Giolito in camp until a week before the Grapefruit League schedule ended, dispatching him to minor league camp before Wednesday’s game.

“Coming up here, my main goals were to make an impression and just try to soak up everything I could,” he said. “… They kept me around, which I’m really appreciative of. I’m just going to keep working hard and take everything I learned with [pitching coach] Mike [Maddux] and talking to the other pitchers and everything, and hopefully make an impact soon.”

Giolito appeared in four big league spring training games, including one start. He logged 6 2/3 innings, allowing three runs and striking out nine while walking three. He impressed the Nationals coaching staff with his pitches, quick arm and demeanor.

“He had a good spring,” General Manager Mike Rizzo said. “It was a good learning experience for him. He got his feet wet with his prospective teammates, his future teammates and I think he learned a lot about what the major leagues are all about. His stuff played out well, and he threw the ball extremely well.”

Nationals fans — and even Manager Dusty Baker — may be salivating over Giolito’s stuff and potential but the team wasn’t counting on him to make the season-opening rotation. The group will be comprised of Max Scherzer, Gio Gonzalez, Stephen Strasburg, Tanner Roark and Joe Ross. The Nationals believe Giolito still has more to work on to be part of that equation.

“He’s close to being big-league ready,” Rizzo said. “I think he has to work on some of the small nuances of pitching. I think the bulk of his developmental curve is complete. But he needs to work on the smaller, little details of preparation, participation and performance in trying to get major-league hitters out.”

It is common, anyway, for teams to keep top prospects in the minor leagues at least 20 days so they can obtain a so-called seventh year of contract control before free agency. Giolito also thinks he has more to improve.

“I’m always working on holding runners, [pitching field drills],” Giolito said. “I feel like I’ve made strides in that over the past year. Another big thing I’m working on is a mechanical adjustment with loading my hips more to get my legs a little more involved and put some more power behind each pitch. Yeah, definitely fastball command is the big thing, especially with the two-seamer now, which is a new pitch this year.”

Giolito will head to minor league camp to continue building his innings count for the season. He hasn’t thrown more than two innings in a game yet this season. Last season was Giolito’s first full season since Tommy John surgery in 2012. The Nationals held him back to start the season and he totaled 117 innings between Class A Potomac and Class AA Harrisburg. Because of his age and previous elbow surgery, the Nationals have a plan for his increased workload.

“We’re going to monitor him,” Rizzo said. “We’ll keep an eye closely on him, like we do with all of our pitchers. We have a plan in place for him and we’ll adhere to it.”

Giolito said he learned a lot from Maddux and fellow pitchers during camp. He said he is armed with a major league-quality game plan for what to improve on while in minor league camp now. And he got more out of the experience than just being a fly on the wall.

“I thought coming in: ‘Oh, I’m a rookie guy. I shouldn’t say much. I shouldn’t do much,'” he said. “I got to be myself 100 percent and kind of feel like a part of the team as much as I could, be myself and laugh and do everything I normally do. I didn’t have to change anything about my personality, which is awesome. And I’m looking forward to doing that coming up here soon.”

Rizzo said Giolito has exuded maturity since he was 17 and drafted 11th overall by the Nationals in 2012. He said Giolito’s mound presence has always been good but “he’s taken that to the next step.”

“He’s very poised on the mound,” Rizzo said. “He thinks he belongs, and he looks like he belongs.”

Giolito could start the season at Class AAA Syracuse. If not, he’ll likely be back at Harrisburg only for a brief time. Should he excel and the Nationals have a pressing need in the rotation, Giolito could be pushing towards the majors. And when that happens, Giolito thinks these five weeks at Space Coast Stadium have helped.

“It’ll be a pretty seamless transition,” Giolito said. “Pitching against the Mets the other night, starting there with a packed house and their starting lineup for the most part, that was a really good experience to kind of take with me going forward. When I do get up there, I’ll feel right at home. I don’t think there will be any nerves or anything like that. I’ve kind of knocked all that stuff out early, so I’m just going to be ready to get called up and contribute.”