It will be what Jordan Pickford does on the pitch that shapes and truly defines his time at Everton.
But, also, it will be how Carlo Ancelotti manages him, how Alan Kelly coaches him and how much pressure Robin Olsen, Jonas Lossl and Joao Virginia put on him. How much they can keep him on his toes and his mind concentrated.
How they all can get the very best out of a talented goalkeeper.
He is, by all accounts, an incredibly single-minded individual when it comes to football. He is assured of his own ability, mentally strong and focused, but he is also human and aware of what has been said.
For the purposes of this discussion, we're not talking about the vile and hideous stuff directed at him - and his family - by the morons on social media, or the excessive reaction to what happened with Virgil Van Dijk.
Yes, it was reckless - "mistimed" as Ancelotti said - and he could easily have been sent off, but done with malice and on purpose? Forget it. Pickford isn't the only one who's gone over-the-top here.
What Pickford will also not have escaped this week, and last, and through parts of last season - and maybe the one before that too - is the criticism he faces for his performances as goalkeeper of Everton and England.
Remember this outburst, last season after the win over Crystal Palace?
“I think the press and everybody; the punters – look at Gary Neville – they just want to come for England players,” he said.
“Everyone gets stick. Some get a lot more praise than others. That’s part of being an England player.
“Everyone hates you, for some reason. I just get on with it. You have got to live with it, you have got to learn. I know what I am capable of and I know what I am good at......
“You just keep it away from your head as the only person who can sort things out is yourself as an individual, on the pitch and in training.
“It’s looking after things on the pitch for Everton that is my main aim. That gets you picked for England.
“It’s funny because everyone raves about you when you are with England but then you get back to your club and everyone wants to slate you.
“As a person, I don’t let it affect me. But it does p*** you off.”
It was a rare insight into how he thinks. It was good. While not everyone will have agreed that he was correct to vent as he did, or react to the flak in the way he had done, or believe that everyone "hates" him, at least he opened up, at least he was showing us the real Pickford.
We need more of that. And that's the point here.
It is what, as he says, he does at training and in games that will make the difference but while his siege mentality is more understandable when confronting criticism at an-England level, does he not need a different approach at club level? He can afford to open up more at Everton.
How many of us - fans, journalists, pundits - who regularly cover the club, know the real Pickford? Or could even say we have a fair handle on what makes him tick, what he thinks about his form, what he's doing on the training pitch and why he is sure he can allay the concerns many have about him? You know? Those worries, that he can go from dropping simple crosses to making saves that defy logic.
It has been lost, somewhat, in the maelstrom of last weekend's derby, that at 2-1 to Liverpool, Pickford's stunning save to deny Joel Matip kept Everton in the game. A game they would fight back to draw.
But you have to wonder that such has been the nervousness around his performances for some time, that even if you took away the Van Dijk challenge, or even transported those set of events into a completely different game, then the discussion would still have been less about his incredible save at 2-1, but how he got away with one in time-added on.
Or at least, the Matip save would not have got a fair look in.
If we knew Pickford better, and he opened up like he did when responding to criticism after that Palace game, then you have to believe there would be more of an understanding of him as Everton's No1.
That when going through these tricky spells, we all knew that the tongue-out reactions were not of someone making light of the situation but, actually, of a player who recognises he's made a mistake but is desperate to put it right.
Those who work with him at Everton 'get' Jordan. They understand him. But other than his manager continuing to publicly show faith, back his goalkeeper and display little appetite for talking about individual errors, what do we really know about the club's No1?
Then again, when social media is as toxic and out-of-control as it is, then you can understand why some are maybe reluctant to speak out and share their thoughts.
If Pickford thinks this, then you couldn't blame him.
Either way, it feels that we all need to hit the reset button and try and make sure there is a connection between Everton's goalkeeper and the club's supporters.
The work of the Everton Fans' Forum and supporter group the County Road Bobblers this week, in gathering messages of support for PIckford in the wake of those disgraceful comments, is a really good start.
Pickford needs to feel the fans' backing, not just on that human level, but on a professional level too. He should take any opportunity he can to speak to them, through whatever medium he chooses, and talk about Everton and his form and anything else that helps create that, as we say, understanding. It would help. His performances are the full answer, but it all feeds into solving the problem of his up and down form.
The modern game has widened the distance between professional footballers and fans but when it comes to the loneliest position on the pitch, the one where mistakes often have the biggest consequences, are analysed like few others and where the margin for error is its smallest, that gap has to be shorter than all others, surely?
Pickford hasn't missed a single league game since he signed from Sunderland in 2017 - that's 119 matches - yet for the last two-and-a-bit seasons, can we say there has been a rapport between the goalkeeper and fans?
In his debut campaign, after which he was named Fans' Player of the Year (as well as Players' Player and the club's Player of the Year), there looked to be the start of a beautiful friendship.
He has remained Everton's No1 but can anyone say we know him any better than we did then?
Because when times are tough on the pitch, there doesn't need to be a siege mentality but a collective one.
Pickford has to take himself back to those award-winning levels of his first season at Everton. That's how good he can be. But it would help if we knew what he was thinking along the way.