Felipe Rivero. (AP Photo/Alex Brandon)

Felipe Rivero had been in Tampa Bay Rays major league camp for four days and was ready to take his physical, the same as his teammates. But instead, on Feb. 13, Rivero was called into an office and told he had been traded to Washington. He was part of the Nationals’ return, that included backup catcher Jose Lobaton and minor league outfielder Drew Vettleson, in exchange for prospect Nate Karns.

General Manager Mike Rizzo said that the Nationals would not have traded Karns for Lobaton if Vettleson and Rivero had not been included in the deal. “A huge-upside left-handed starter,” Rizzo said after the trade. The Nationals have been particularly bullish about Rivero, a lean, 22-year-old left-handed starter from Venezuela with an easy delivery and whose fastball can touch the mid-90s.

“I’m going to keep working here like I did in Tampa,” Rivero said in Spanish. “Nothing changes. It’s the same baseball, just a different team.”

Livan Hernandez, the former Nationals pitcher here as part of the coaching staff, is extremely high on Rivero. “He’s going to be a superstar,” he said earlier in camp, perhaps a hyperbolic spring prediction. Pitching coach Steve McCatty added: “He’s got a live arm. Lot of movement.”

Rivero is still adjusting to his new surroundings. On Thursday morning, he sat quietly at his locker, back to the clubhouse, playing with his cellphone. He is surrounded by other Latin players and talks with them often. But, he has only been here two weeks. 

And on the mound, Rivero still has to improve. He has spent five seasons in the minors, the majority as a starter, and has a career 3.45 ERA and 2.72 K/BB ratio. He was named to the 2012 Futures Game. He throws a fastball, with cutting action, along with a curveball and change-up. He admitted that his change-up is his second best pitch and his curveball is still a work in progress. He hopes to improve his consistency with the pitch and location. “I have to keep working on my curveball and see what happens,” he said.

Last season, he posted a 3.40 ERA over 127 innings spread over 25 games, 23 of them starts, at high-Class A Charlotte in the Rays system. He posted a 6.4 K/9 rate but a 3.7 BB/9 rate, so his command needs work, too. He pitched for the Leones del Caracas in winter ball in Venezuela, allowing five runs over 5 2/3 innings as a reliever. He said he was used to face left-handers did well. He also to improve facing right-handers, too. This is where a polished curveball would help, he said.

Rivero is unsure what level of the Nationals minor leagues he will begin in nor what role the organization wants him in. But, he views himself as a starter. “If they need me to relieve, I’ll do the same as I did before,” he said. “If I have to adjust, I’ll do it.”