Severino, 22, was hitting .246 with five home runs and 34 RBIs in 91 games at the time of his promotion.
Severino was pleasantly surprised after learning Monday night that he was going to the big leagues for the first time. The first person he called was his mother, but he had a tough time reaching her over the phone. Severino was able to contact his father, however, and he was overjoyed and cried after hearing the news.
While he is with the Nationals this month, Severino said he wants to improve at the plate.
"I need to be better with the offense," Severino said. "I need to close my shoulder, hit the ball up the middle."
Uggla returns to the Nationals after missing 22 games because of back spasms. He played in seven games on a rehab assignment, making stops with Class A Hagerstown, Class A Advanced Potomac and Harrisburg.
Joining the Nationals' bullpen for the fourth time this season, Solis returns to the Major Leagues after posting a 2.03 ERA in nine games for Syracuse.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.