I actually think that play matters. So do many others that don't result in goals.
It was a mistake by Mangala. He mis-judged the trajectory of the ball. That the striker also mis- judged the trajectory of the ball is frankly irrelevant. Mang's job is not to defend whwn the striker is doing the right thing, its to defend all the time. If he didn't misjudge that ball, it would have been an easy clearance. Actually it could have been a controlled headed pass to one of the 4 City players in the vicinity.
But instead, that unforced error led to a breakaway. The post discussion of Otamendi moving into his position or Clichy closing in, is more after the fact hubris. At that point Gladbach controlled play, and based on City's movements they could have made different decisions. Ota could have moved closer and the point of play switch to create something just as dangerous.
Point here i s this, there was only 1 point in that sequence in which City had a 50/50 chance, Mang had it, and messed it up by overrunning the play coz he was closing the striker and not focussing on the ball.
Everything beyond that point was always advantage Gladbach. Sure Yaya could have moved more aggressively, Otamendi could have squeezed the space, kolarov could have stayed with his guy, e.t.c. But the only significant error occurred on the 50/50 ball.
To that effect, Pudge is right. It was Mang's mistake.