If I may offer a differing perspective, I think our new system might be exposing Sterling's weaknesses quite abit. Weird thing to talk about, considering he didn't play this match, but I was thinking about how our wingers are a little erratic this season (except Foden).
---Stones----Dias----Zinny----
------Cancelo---Rodri--------
-------KdB-------Gundogan----
---Mahrez----Gaby----Sterling---
For eg. this is how we usually set-up on the attack. Our wingers are pushed high and wide, as per usual. However, this season it's much more apparent we are playing without attacking/overlapping FBs, the trade-off for more midfield numbers and defensive stability.
I think the current system requires more technical demands from our wingers to beat a man on their own, because there's one less man to support them on the attack. Way I see it, for the wingers this season it's like "here's the ball, pass it back, put a cross in or you're on your own." To put it more simply, they are made to do more dribbling than off-the-ball running.
Sterling's technical ability has never been his strength. I believe he's at his best when there's players playing close to him and combining with him (Silva, Mendy, etc). Which is why I think players like Foden, who are technically gifted and can consistently beat their man, slot better into the current system, and I would say the proverbial 'eye test' would suggest that.
I'm sure I can explain better, but I'm not a particularly articulate person... I'm not making excuses for/having a go at Raz, but just hoping to get a more educated guess on his dip in form.