Nats calling up Nathan Karns to start tomorrow, Cedeno sent down

Needing a guy to start tomorrow in place of the injured Ross Detwiler and without many attractive options at the Triple-A level, the Nationals have decided to call up right-hander Nathan Karns from Double-A Harrisburg. Karns will make his major league debut at Nationals Park against the Orioles tomorrow night. To make room for him on the active roster, left-hander Xavier Cedeno, who was called up today, will be sent back to Triple-A Syracuse. Karns, who is already on the Nats' 40-man roster, was the Nats' minor league Pitcher of the Year last year, splitting the season between low Single-A Hagerstown and high Single-A Potomac. Baseball America ranked him as the Nats' No. 5 prospect coming into this year. The 25-year-old righty has made just nine starts at the Double-A level, going 4-2 with a 4.60 ERA, 55 strikeouts and 18 walks in 45 innings. Karns went just 1/3 of an inning three starts ago, but has gone six innings each of his last two outings. He allowed five runs (four earned) on eight hits with nine strikeouts and one walk his last time out. "He's one of the good young arms in the organization," manager Davey Johnson said. "He's been throwing the ball pretty good lately." Karns is a talented pitcher with a power arm. He throws in the mid-90s with a good spike curveball, a slider and a changeup. Still, the Nats would prefer not to have to call on a guy who has made just nine starts above high Single-A to start a big league game against a potent offensive club. "It'll be a good test," Johnson said, when asked if Karns is ready for this jump. "We'll find out. First time out in spring, he threw the ball good and then got a little anxious. But he's got a great arm." Karns had shoulder surgery in 2011 and made just 13 starts in 2011, but performed well last season, posting a 2.26 ERA in 13 starts at high Single-A Potomac. He got his first taste of big league spring training this year, and started off great, throwing two scoreless innings against the Mets, allowing a hit and striking out three. His final two appearances with the Nats this spring were rougher; he walked two in an inning at Jupiter against the Cardinals and then went just 2/3 of an inning against the Cardinals on March 8, allowing four hits and seven runs (one earned). With Chris Young struggling, Ross Ohlendorf not on proper rest to pitch tomorrow and Karns already on the 40-man, the Nats decided to go with the inexperienced but talented righty, a guy Johnson said was among the Nats' top three options to step into the rotation if a starter went down. He'll take the mound in front of what should be a crowd of over 40,000 tomorrow, looking to deliver a big game on a stage he's likely dreamt of for years.