Warning: this is a long read!
I've got Villa fans in the family, and when I asked one just after he joined how many goals I should bet on him scoring this season, the response I got was "if he hits double figures you'll be lucky".
As others have said, he didn't hit a high volume of goals at Villa, and it's not like Villa had a bunch of clinical strikers to carry that burden. Over the past couple of years he's worked on his goalscoring and slowly improved - I think he can continue to do this and may well show steady improvement, but will never deliver really big numbers. Yet strangely, I never heard Villa fans complaining about his lack of goals. He may not have scored many, but they as a team scored more and won more when he was there.
I think it can be helpful to distinguish between position and role. Let's say position is the part of the pitch a player spends most of their time, and where they can generally be expected to be in relation to their teammates, especially out of possession. And role is their function within the team - what purpose they serve, and what they're expected to deliver.
For example, Cancelo and Zinchenko can both play in the position of left-back. And while of course there's overlap in what they're expected to do, there's a pretty clear difference between what each of them delivers, and you can understand an argument for playing one or the other based on the make-up of the rest of the starting XI and the expected strengths and weaknesses of the opposition.
Or, in the centre forward position, you might deploy someone in the role of striker or in the role of false 9. That might be a tactical decision, or just based on which players you've got available. But either way, you know which role that player is playing, and you judge his efficacy against the expectations for that role.
For both Villa and City, Grealish has played in the left forward or left wing position. If you were to draw out the formation of each team with him in, his location in that diagram would be broadly the same.
The most common role played by players in that position is one that consists of maintaining width to stretch the pitch, going past full-backs with pace and trickery, whipping in crosses and moving into the middle to score goals.
I think we as fans, and perhaps also as a club, are expecting Grealish to perform that role right now. And because he's a talented and hard working player, he's doing OK.
But that's never been his role, and it doesn't play to what his actual strengths are. Yeah, he's always done a bit of that stuff, but his role - his function and purpose within a team - lay elsewhere. At Villa, his position may have been left forward, but his role was all-over-the-pitch playmaker. He was Dean Smith's get out of jail free card, a player who could exist in a tactical vacuum and make stuff happen, improving the performances of all the players around him because of the space, time and service he provided. His runs and passes from deep, his ball retention, his constant and consistent creativity, and the way he used those qualities to relieve pressure and force transitions - that was what made him special for Villa.
All the information we have around the Grealish transfer tells us that Guardiola's been aware - and a fan - of him for years. He's watched and researched him thoroughly, what he was doing for Villa and how he was doing it. And after all that watching and research, he and the club decided that they wanted or needed him so badly that they were willing to break the British transfer record to do it.
I refuse to believe that we bought Grealish thinking he's a lightning-quick winger who's full of goals. He was incredible for Villa, but he wasn't those things. We could have bought another player with that skillset for maybe half the price, and that's not even taking into account the players we already have who can perform that role.
I think that by the end of his City career he will have either been moved to a different position - one that's more suited to the kind of role he's best at - or his role in that left forward position and the roles of some of the players around him will have been tweaked to adjust to how he best performs and how the team best performs with him in it. He's never going to play exactly the same role as he did for Villa, because nobody has that kind of freedom under Pep. But we surely didn't buy him to be a left forward in the traditional mould.
