Michael Laudrup admits Swansea could be without Michu for as long as three months when the forward eventually has to undergo ankle surgery.
The Spaniard missed a month of action after hurting his left ankle in the derby defeat at the hands of Cardiff in November, but it is a long-standing problem in his right ankle which has rendered him doubtful for Sunday's clash with Everton.
Laudrup has revealed the 27-year-old will require an operation, but stated it is a problem the player could yet complete his career with.
However, Michu's obvious frustrations at his inability to produce his best form due to the injury could mean an operation comes sooner rather than later.
Swansea manager Laudrup says the club are weighing up information from their medical team before making a decision, but revealed in a worst-case scenario he could face three months on the sidelines, depending on the nature of the surgery required.
A lay-off of that length would effectively end any lingering hopes the former Rayo Vallecano man has of making Spain's World Cup squad, having won his first cap in October.
Laudrup said: "I've had one or two conversations with him, but we haven't made a decision yet.
"We're taking in all the information.
"There are two kinds of operation (keyhole and then more detailed) and we still need some information, but in the worst case it is three months."
But the Dane does not believe the World Cup in Brazil is in Michu's thinking when it comes to the injury.
"He wants to be fit. He's not thinking about the World Cup," said Laudrup.
"Even if he is 100 per cent fit, he knows it will be very difficult to get into that squad.
"He's competing with Fernando Torres, Alvaro Negredo, Fernando Llorente and David Villa.
"He's just frustrated that he hasn't been able to perform at his best level because he has played a lot of games at 80 per cent of his physical ability.
"He's angry at himself because of the injury."
Laudrup will wait as long as possible to see if Michu is available to face the in-form Toffees, but admitted his build-up has not been ideal.
"I don't know if he can play in the short term," said Laudrup. "We will try to get the information as quickly as possible.
"He hasn't trained for two days.
"He played at Norwich on Sunday. We were off Monday and Tuesday, he trained on Wednesday, but it hurt on Thursday, even walking.
"We will see on Saturday and decide."