David Moyes has suggested Jordan Pickford could be worth as much as £30million, with the Sunderland manager rejecting "derisory" valuations of the highly rated goalkeeper.
Pickford has been one of the few bright sparks in a dire campaign, with Sunderland relegated to the Championship after 10 years in the Premier League.
The 23-year-old has been linked with a raft of clubs, including Liverpool and Everton, although Arsene Wenger ruled out a bid to bring him to Arsenal.
Pickford was called up to the senior England squad for the first time in October and Moyes indicated Sunderland will be looking for a substantial fee for their prize asset.
"It would need to be a really, really big offer," said Moyes.
"I have said all through the season that sometimes on your journey, you may have to sell to improve.
"But I have heard some really derisory sort of figures getting mentioned and it wouldn't be any of those figures, I can tell you that."
MOYES: "Didier Ndong is under contract and he's improved. He's younger than @JPickford1 and he's had a good first season."— Sunderland AFC (@SunderlandAFC) May 19, 2017
Only one goalkeeper has ever moved for a fee in excess of £20million, with Gianluigi Buffon's £33million transfer from Parma to Juventus making him the world's most expensive stopper.
But, asked by reporters if Pickford's fee could rise as high as £30million, Moyes said: "Yes. He has been our highlight.
"For a young boy to break in and perform like that. The other night he was fantastic against Arsenal.
"Nearly everything was perfect and we will need him again this weekend at Chelsea."
|McIlroy suggests limiting alcohol sales after Bay Hill abuse|
|Marotta dismisses Allegri-PSG links as Juve focus on Can|
|MLS Review: Champions Toronto still winless, Atlanta crush Whitecaps|
|Lukaku: A lot of players will join Manchester United next season|
|I feel like I just woke up – Indian Wells finalist Federer explains slow start|
|High-flying Reds win third straight in Buenos Aires|
|Salah and Liverpool don´t fear Man City: We´ve beaten them!|
|What can I lose? - Mourinho defends criticism of Man Utd players|
|Mourinho accuses Manchester United of being scared to play|
|Mourinho delivers stinging Shaw criticism after FA Cup win|
|Haskell: England not good enough during Six Nations|
|Allegri waits on Chiellini update after Juve´s SPAL stalemate|
|Stenson leads by one with DeChambeau and McIlroy lurking|
|Racing put pressure on leaders Montpellier as Toulon are toppled|
|Klopp eases concerns over Can´s back complaint|
|Six Nations defeats make no difference to England mindset – Hartley|
|Matic was an island of personality - Mourinho questions United mentality|
|Del Potro demolishes Raonic to set up Federer final|
|He´s getting quicker on the Zimmer frame – Schmidt jokes about Best future|
|SPAL 0 Juventus 0: Scudetto charge halted by Serie A strugglers|
|Manchester United 2 Brighton and Hove Albion 0: Lukaku & Matic book semi-final spot|
|Fresh rib fracture for Cavendish but ´no serious injury´ after crash|
|Unbeaten Federer fights back to reach Indian Wells final|
|Klopp: Salah could be among world´s best, but don´t compare him to Messi|
|Woods hopes to still be within reach at Arnold Palmer Invitational|
|Championship Review: Wolves on the charge as Monk lifts Birmingham´s spirits|
|Twickenham boos will ´put me to sleep at night´, Jones claims|
|Salah threatening Rush´s record for goals in single Liverpool season|
|Hodgson hopes Zaha avoided injury|
|Snow causes Wakefield-Widnes abandonment|
|Liverpool 5 Watford 0: Inspirational Salah nets four as Reds bounce back|
|Lambert rues Everton´s ´offside´ opener in costly Stoke City defeat|
|Scotland´s late rally leaves Townsend feeling positive for the future|
|Wales hold off France to claim second behind Ireland|
|Man Utd bench Pogba & Sanchez for FA Cup quarter-final|
|Pardew: Evans loss key to Bournemouth defeat|
|Zarco breaks track record to claim Qatar pole after Rossi crashes in practice|
|Ireland had to make every moment count against England – Best|
|Salah breaks Torres´ impressive Liverpool record|
|We are not heroes one day and villains the next – Mourinho continues defence of Sevilla exit|
|Lions bounce back against Sunwolves, Stormers end miserable streak|
|Jones: England losing streak only natural|
|They have many players who´d get in my team – The Sevilla stars Mourinho should buy|
|Mario Gomez will not beg for World Cup place|
|England´s form continues to run cold in Twickenham snow|
|Nibali holds on in Milan-San Remo as Cavendish crashes again|
|Bournemouth 2 West Brom 1: Stanislas piles misery on Pardew|
|Buffon to play on for Italy as Di Biagio calls up uncapped duo|
|Huddersfield Town 0 Crystal Palace 2: Tomkins and Milivojevic secure priceless win|
|Stockdale makes history as ruthless Ireland win Grand Slam|
|Stoke City 1 Everton 2: Tosun at the double after Adam´s early dismissal|
|Simeone insists Atletico can survive injury crisis|
|Ireland´s Stockdale breaks Six Nations single campaign try record against England|
|Leipzig out to halt Bayern celebrations at Red Bull Arena|
|NFL Draft 2018: Jets acquire number three overall pick from Colts|
|Board accepts responsibility for West Ham woes, Brady claims|
|In-form Eriksen hopes he hasn´t hit Tottenham ceiling|
|Roma boss Di Francesco happy with Messi, Barca challenge|
|Bangladesh warned over ´unacceptable´ Colombo behaviour|
|The directors know where to find me - Gattuso awaits Milan talks|
|Laidlaw breaks Italian hearts in Rome|
|UMBC´s March Madness win earns everyone in USA free pizza|
|Zidane focused on Real Madrid players, not Neymar|
|Mourinho´s United rant recalls unhappy Madrid demise|
|Swansea City 0 Tottenham 3: Eriksen leads Kane-less Spurs into FA Cup semis|
|Valverde not worried about Barcelona legacy|
|Markelle Fultz´s return remains a mystery to Brett Brown|
|Bale is happy at Real Madrid, says Zidane|
|Spalletti seeks consistency as Inter prepare for final push|
|Absence of ´best in the world´ Busquets makes Rakitic key for Barca|