By Patrick Andres The Aggies’ new offensive coordinator spent just 20 days with the Rebels. Texas A&M is hiring UNLV offensive coordinator Bobby Petrino as its next offensive coordinator, according to a Wednesday afternoon report from Chris Low of ESPN. Petrino, who will replace fired offensive coordinator Darrell Dickey on coach Jimbo Fisher’s staff, departs Las Vegas after just 20 days with the Rebels. He was named UNLV’s offensive coordinator Dec. 15 under new coach Barry Odom. The Aggies averaged just 22.8 points per game this season, ranking 101st out of 131 FBS programs. Petrino has had …