Emery surprisingly left Bernd Leno on the bench despite Arsenal spending £20 million ($25.5 million, 22 million euros) on the German 'keeper from Bayer Leverkusen in June.
According to reports in the Star, Unai Emery is unhappy with the weight of some of his players in the Arsenal squad and believes they are "too fat".
Leverkusen's English Twitter account responded by posting a video of Bernd Leno - who joined Arsenal from the Bundesliga club in pre-season - beginning a passing move that ultimately led to a goal, with the caption reading: "In case you were wondering how to play out of the back".
He attempted more passes against Man City than in any game he played in last season but conceded possession to Pep Guardiola's team 11 times.
After taking over from Arsene Wenger, Emery has emphasised the importance of using the goalkeeper to help play the ball out from the back, and it was clear that his players are still getting used to the new system. Petr Cech can continue to start the match, I believe in him.
Emery, however, has been handed a timely boost ahead of only his second Premier League outing.
"I am very happy with his performance", Emery said of Cech. This week Nacho Monreal is working every day, training every day with us.
However, Lehmann said he was "surprised" that Cech tried to play out from the back so often against City. I want in each moment to know what is our best action to do in the match.
"We are continuing this work and against Chelsea we are going to analyse the opposition. The game dictates what to do and not a certain style you have to play".