The Spanish third division side could go out of business by November 17 if they do not raise €2 million [£1.5m]. But the England-based players, all of whom started their careers at the struggling team, are aiming to help.
Michu, who started his career at Oviedo and stayed there between the ages of five and 21, confirmed that all three had contributed, telling reporters: "Myself, Mata and Cazorla have all bought shares, but it would be wrong of me to say how much.
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Michu, who joined Swansea City for £2m (€2.5m) in the summer, hopes that Oviedo can experience a similar revival to that of his current side, the Swans themselves almost having gone out of business 10 years ago.
"Swansea fans should know how much it means to me and the Oviedo supporters," the Spaniard continued.
"I remember reading up on the history of Swansea when I first arrived here; I remember reading how the Swansea supporters bought shares in this club when it was in trouble 10 years ago - and again many years before that.
"And look at the club now; in the Premier League and winning at places like Anfield. Hopefully this SOS can have a similar reaction."