Venezuelan left-handed reliever Felipe Rivero was activated Thursday by the Nationals, occupying an important role. He joins Matt Thornton as the only two southpaws in the Nationals bullpen. Rivero got the news from Triple-A Syracuse. Manager Billy Gardner told him after the road trip yesterday. Rivero arrived in a four-player trade with the Tampa Bay Rays prior to spring training in 2014. He made 14 starts with three teams in the Nationals' system last season. "Real surprised, didn't realize (I) was going to get called up so quickly," Rivero said through team translator Octavio Martinez. Martinez said Rivero "feels real comfortable, like he's been here before because of spring training and preseason games. He's relaxed." Martinez said Rivero will use that familiarity from spring training with the Nationals, and that is where he worked exclusively as a reliever. "Big thing was moving him to the bullpen," Martinez said through translation from Rivero. "He was able to control a little bit more his motions. He just kind has to get warmed up, doesn't have a lot of time to think about things. That has helped with his arm slots, just getting in there and throwing the ball."

Nationals director of player development Mark Scialabba said they liked what they saw from Rivero during spring training. "Obviously electric arm. The fastball comes out good," Scialabba said. "He jumps on hitters and its just matter of him harnessing his stuff and just getting repetition. He certainly opened some eyes in spring training and had a great camp. He showed the ability to throw strikes and utilize his fastball, slider combination and a changeup as well that can play up here." And Scialabba said because he began as a starter, he wasn't brought in to just get one guy out. "The big thing is he doesn't worry about who is hitting, whether it's a righty or a lefty, he just aims at that (catcher's) glove," Scialabba said. "If he's able to do his job, his ability should take over. "He's going to try to focus on the same thing he was doing in spring training where he wasn't worried about the hitter, just doing his own job and what he has to offer and his ability and hopefully that takes over," Martinez said. Nationals manager Matt Williams said the way he commanded the fastball and the good velocity caught his eye. "He's powerful. We put him in the relieving role over the last six or seven times on the mound," Williams said. "Three (games) at the end of spring training, a couple more in the minor leagues. He's gone back-to-back down there, so we feel confident in that regard. What he's shown us is he's throwing the ball over the plate, it's mid-90s fastball with breaking ball and changeup. We need another lefty, so he's a logical option for us. Power lefty out of the pen." Scialabba said Rivero will be able to show his versatility with his ability to pitch to more than one batter. "We want to be able to provide value for us with some length as well," Scialabba said. "If he's going to pitch, we want him to pitch full innings. We don't want our pitchers at all to be just specialists. We want them to be able to utilize their stuff and pitch to both sides of the plate have the ability to get both righties and lefties out."