LAKELAND, Fla. -- Nate Karns' scheduled bullpen throwing on Sunday didn't happen because he developed what the club characterized as tightness in his upper right leg. The Nationals' Minor League pitcher of the year for 2012, Karns is effectively shut down until the club receives a second opinion about his problem. The tightness developed after his first spring appearance. He's had three outings totaling 3 2/3 innings.
He had been a candidate to assume Gio Gonzalez's place in the spring rotation if Gonzalez's time with the USA World Baseball Classic team was extended. Ross Ohlendorf, who has pitched eight innings in three appearances, is the other Spring Training understudy candidate for Gonzalez.
Marty Noble is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.