Nicolas Otamendi was singled out for handball in the box, but with the decision taking almost three minutes to make, most were again underwhelmed
The Video Assistant Referee [VAR] was once again in the firing line after another controversial night in the Champions League.
UEFA brought forward the use of the technology for the last-16 stage of this season's competition , and the controversial system has caused more consternation.
In the first round of fixtures, Ajax were furious after their opening goal against Real Madrid were ruled out for a controversial offside call .
Now the referee for Manchester City's first leg trip to Schalke, Carlos Del Cerro Grande, was at the centre of the confusion after a penalty was awarded to the home team in the first half.
Leading via Sergio Aguero's goal, the hosts had the chance to draw level when Nicolas Otamendi handled Daniel Caligiuri's goal-bound shot.
A corner had seemingly been awarded but VAR intervened to give a penalty, delaying the game being restarted by nearly three minutes before Nabil Bentaleb was permitted to step up to make it 1-1.
Commentating on BT Sport , former Arsenal defender Martin Keown lamented: "It is the length of time this is taking.
"The spontaneity of football is in danger of being lost here. We want quicker decisions, please."
Rio Ferdinand, formally of England and Manchester United, added: "This is the problem with VAR. It takes so long to make a decision."
And he was not the only one to be confused by the time taken to make the call:
Central to the delay was a problem with the pitch-side screens which officials can refer to help make decisions.
Those monitors were out of action which prevented Cerro Grande from giving an immediate decision, forcing the significant delay in Gelsenkirchen.
By the end of a remarkable opening 45 minutes Schalke had turned the game around when Bentaleb struck home a second penalty after Fernandinho was adjudged to have tripped Salif Sane - this time given without the assistance of VAR.