It is a common thing for Koeman - trying to guess what the best thing to do is and then having to sub/change formation after a portion of the first half makes it evident that his lineup and/or tactics were wrong
People give him credit for the quick changes normally, I've always been worried about him getting it wrong in the first place
I don't think he really got it wrong from the outset on Saturday in terms of the system.
Clearly, the plan was always to go with a back three.
However, with the injuries to two players key to that (Coleman and Mori) it meant that the personnel who came in (Pennington and Holgate) had to play out of position or - rather - against a side that blatantly targeted that area of the pitch, and neither the more experienced players nor the manager then did enough to try and nullify that threat.
Kind of what
@Eggs is saying.
We came out strong after half-time, and if he had made the change to a back four then I think we'd have made more chances.
That being said, their third goal - which is what killed the game - had absolutely nothing to do with tactics or system.
It was crap play from Williams and Jagielka who put Pennington and Holgate in a bad position.
The youngsters flapped, lost possession and then Robles was utterly useless as well.
Kind of like in the Spurs game, for all this talk of tactics etc, the goals really boiled down to basic errors.
Mane's was a great run but could easily have been stopped. Coutinho was allowed to run into the area.
That's not tactics. That's players not doing the basics.
At home I back us against anyone at the moment but I do think - away from home - he is maybe trying to shift to another style that the players we had available on Saturday weren't able to play.