Manchester City and Borussia Dortmund both progressed to the Champions League knockout stage after a largely uneventful 0-0 draw at Signal Iduna Park.FULL MATCH DETAILSCity went closest to breaking the deadlock when Riyad Mahrez's second-half penalty was saved and they remain unbeaten and are assured of top spot in Group E with one game to play.The point was also enough for Dortmund, who were intent on keeping a clean sheet after having the better of the first half, and they too are guaranteed a place in the last 16.Guardiola handed goalkeeper Stefan Ortega his club debut and England defender John Stones returned to action for the first time in seven matches after recovering from a hamstring injury.Nathan Ake, Ilkay Gundogan, Julian Alvarez and Phil Foden also returned to the starting line-up, while Ederson, Kevin de Bruyne, Jack Grealish, Bernardo Silva, Manuel Akanji and Aymeric Laporte were all rested.With City already assured of their place in the knockout phase and a point good enough to see Dortmund through, the opening exchanges lacked any real tempo.City goalkeeper Ortega made his first save with his legs in the 16th minute when Karim Adeyemi stayed on side to run through on goal.Adeyemi was instrumental again as Dortmund began to stretch City's back four, first picking out Giovanni Reyna on the left edge of the area after a flowing move, but the latter's curling effort was well held by Ortega.Germany forward Adeyemi then produced an excellent low cross into the path of Youssoufa Moukoko, who let the ball run across him before side-footing wide.Teenage striker Moukoko combined with Adeyemi again and forced Ortega into another save.City had 66 per cent of first-half possession, but never troubled Dortmund