PITTSBURGH (AP) — Jordy Nelson caught the ball, spun and prepared to dart downfield.Two steps later, Green Bay’s Pro Bowl wide receiver was on the turf, his left knee injured and his season very much in doubt. While Nelson was able to gingerly walk to the sideline early in the first quarter of Sunday’s 24-19 exhibition loss to Pittsburgh, it might be the last sign of Nelson in his familiar No. 87 jersey this year.While Packers coach Mike McCarthy stressed the defending NFC North champions “will look for good news” when Nelson is re-evaluated in Green Bay on Monday, quarterback Aaron Rodgers expressed equal parts frustration and mystification.“It’s difficult to lose a guy like that in a meaningless game,” Rodgers said.The play that may change the course of Green Bay’s season started innocently enough.