Cedric Evina's dreadful defensive error and Harry Forrester's senseless red card contributed to Doncaster's 3-0 defeat at new leaders Bristol City.The home side went in front after 13 minutes when Aden Flint's header from a free-kick caused havoc on the edge of Doncaster's six-yard box. Kieran Agard's attempts to force the ball home were foiled, but Aaron Wilbraham followed up to net from close range.The second goal on the half-hour mark was a personal nightmare for Rovers left-back Evina, who dwelt disastrously on the ball on his own goal-line, allowing Mark Little to slide in and score.Agard wrapped up the points with a deflected shot in the 82nd minute after being set up by the impressive Joe Bryan.Doncaster had claimed an early penalty when Forrester went tumbling, but acting on a linesman's flag, referee Michael Bull booked him for diving.Despite having been cautioned, Forrester stupidly kicked the ball away when City were awarded a 51st-minute free-kick and earned an inevitable second yellow card.