Gary Neville believes that Manchester United must find a top-class goalkeeper if they are to challenge Man City and Liverpool next season.
David de Gea was United's first-choice goalkeeper the last time the Reds won the Premier League.
The Spaniard has been the number one ever since the 2012/13 title-winning season under Sir Alex Ferguson. However, his place in the team has been called into question in recent years as the number of mistakes he has made increases and his match-winning contributions become less frequent.
Dean Henderson impressed during loan spells with Sheffield United, and he returned to Old Trafford in the summer with the intention of unseating De Gea as the starter.
That is yet to happen, and Neville believes that if United are to close the gap to City, Ole Gunnar Solskjaer will gave to find a top-class goalkeeper.
"Your goalkeeper, to win a league, has got to be exceptional," he told The Webby and O'Neil YouTube channel when asked what Solskjaer's number one transfer target should be this summer to build a title-winning team.
"I said three, four years ago, and at the time Jurgen Klopp took me on publicly, 'you'll never win a league with Karius and Mignolet'.
"That's not to say they're not good goalkeepers and decent goalkeepers, but which team do you know that wins the league without a great goalkeeper or goalkeepers with great seasons?
"Ederson is a great goalkeeper. Petr Cech was a great goalkeeper. [Peter] Schmeichel, Van der Saar. Even Kasper Schmeichel for Leicester. David Seaman. You go through all the years, you've got to have a top goalkeeper. And Alisson is a great goalkeeper.
"So you think about goalkeepers and we have to start asking questions about David de Gea.
"You have to start asking questions about him because the mistakes are coming now, I wouldn't say thick and fast, but they're coming more regularly and they cost points and the game-winning saves are coming less, in my opinion, the one-on-one saves are coming less. I think that has to be a question that Ole has to answer.
"And then there's the question of Henderson. Are we saying Henderson is going to be the number one for Manchester United?
"What I would say now is, if Pep Guardiola or [Jurgen] Klopp came into Manchester United in six months' time, they would bring a new goalkeeper in that would remove all doubt as to whether he was great or not.
"That might be tough on the boy Henderson, but I think to chance it, to gamble on winning the league."
On how Solskjaer should handle the goalkeeper position during the remainder of the season, Neville added: "You've got to get your keeper right? So that's the first question: is the keeper right?
"And I would say that David de Gea, in the next four or five months, I wouldn't leave him out until the end of the season. I'd keep him in - although there is a point to say: 'do you find out about Henderson in this last three months of this season? Do you find out whether he's top-notch?'
"So there is a case for that, but I think David de Gea deserves to finish the season as number one and prove that he can get back to that level he was at before."
