What Pep did last night was play what could be called a pseudo back 3. Laporte wasn’t a left-back in the sense of getting forward and supporting Sane, as Zinchenko or Mendy would have done. He was a pure defender. Had Delph played, more likely he’d have tucked into midfield allowing Silva to support Sane. That’s worked so well for us this season.
That meant our width on the right came from Walker, who had a shocker of a game & got caught upfield giving the ball away for their first goal. On the left, Sane had space but did fuck all whenever he recieved the ball. The young lad Alexander-Arnold kept his head and didn't allow Sane to get past him. Leroy didn't help himself mind you by coming inside almost every time. Had he mixed it up a bit he could have introduced an element of uncertainty to the full-back but he didn't so the lad was quite happy to show him inside, where he had support from his midfield.
Gundogan didn't seem to know what to do, in a role he should never have been asked to play, which was a kind of old-fashioned right-half. That's not pragmatism; it's pissing about to create a system that had no discernible benefits and many downsides. Even Silva had an air of "WTF am I supposed to do".
He either sticks with the 4-3-3 or, if he wants to be a little more cautious (i.e. pragmatic), plays a flat back four (with Danilo at left back) and the two in the defensive midfield positions, maybe sacrificing Jesus and having Silva in the false-nine role he plays for Spain. Or Sterling. Or he could have KDB and the two Silvas behind Jesus, leaving Sane on the bench. What he ended up doing was neither one thing nor the other.