The Atlanta Braves have called upon another prospect to fill the gap on Thursday afternoon. JR Ritchie is being added to the 40-man roster and will take the mound to start the series finale against the Washington Nationals, sources close to Atlanta Braves on SI have said. Didier Fuentes took the mound on Wednesday in the Braves' first attempt to give the rotation extra rest. However, he only lasted three innings, forcing the Braves to turn to Martin Pérez for a long-relief role. He had been penciled in to start on Thursday. This was a possible scenario that was speculated on ahead of Wednesday night's game. The Braves ultimately had to pivot, but they have an option to turn to. Ritchie has looked sharp for Triple-A Gwinnett so far this season. He owns a 0.99 ERA, a 1.02 WHIP and 28 strikeouts across 27 1/3 innings pitched. He was in big league camp for all of spring training, building a case for a call-up. However, the Braves opted to give him the first month to refine himself further in Triple-A.…