Manchester City could face a battle to keep Raheem Sterling, with Real Madrid, Barcelona and Paris Saint-Germain all interested in the England star.
The 23-year-old winger, who earns an estimated £180,000 a week and could command a £100 million ($140 million, 114 million euros) transfer fee, is under contract at the Etihad until 2020 but City manager Pep Guardiola understands Sterling is a tempting target for rival teams.
"Maybe other clubs are interested - anything can happen - but he knows how important he is to us," said Guardiola.
"For contracts I'm not the guy, it's Txiki (Begiristain, City's director of football). No doubt it's important, the deals of the agents and the circumstances."
Sterling had been in negotiations to extend his contract following in the path of team-mates Kevin De Bruyne and David Silva, who have both signed extensions in recent months.
Sterling has been in superb form this season, scoring a career best 20 goals in all competitions, 10 behind top scorer Sergio Aguero, with City having all but wrapped up the Premier League title.
That form appears to have secured Sterling's place in England manager Gareth Southgate's World Cup squad, but has also alerted City's rival European superpowers to Sterling's qualities.
Real were interested in Sterling before he left Liverpool in 2015 and could resurrect their pursuit.
Aguero 'so important'
Meanwhile, Sergio Aguero is set to miss Saturday's match at Everton, when City could go 19 points clear and take a huge step towards landing the title.
The Argentina international, who is recovering from a knee injury sustained three weeks ago, posted a social media picture of himself on an exercise bike just before Guardiola's press conference on Friday.
Aguero missed Argentina's two recent friendlies in the international break, against Italy and Spain, as well as City's 2-0 win at Stoke City on March 12.
"He is much better. We'll see tomorrow," said Guardiola.
"The problem with Sergio is he is so important for us."
With Aguero doubtful, Guardiola has given a vote of confidence to Gabriel Jesus, with the 20-year-old having scored just once in his last 15 games but hit the winner for Brazil against Germany on Tuesday.
"First of all that's important for him to score after a long time injured - strikers need goals."
City will be without defender John Stones, who came off during England's 1-1 draw against Italy.
"John Stones had concussion in the last game, he feels really good but the rule is seven days off so he's not available," added Guardiola.
City can go within one win of securing the title with victory at Goodison Park but Guardiola is taking nothing for granted after they lost 4-0 there last season.
"It's not already done! We need two or three wins but we are in a good condition with eight games left, 16 points ahead and a healthy goal difference," he said.
"Believe me, I am preparing for Everton like it's the most important game we have to play.
"At home Everton are strong. I don't like to analyse what happened last season."
Guardiola added: "We didn't play well there and lost 4-0. This season's result (at home) was much better but tomorrow is another game.
"You prepare for the next games, you have to be ready. We've been three weeks without playing, a week in Abu Dhabi then a two-week break and I don't know how we'll react. I hope we will be at the same level as we have been all season."