Sporting president Frederico Varandas has confirmed that striker Viktor Gyokeres will face disciplinary proceedings at the club after failing to turn up to training on Saturday.
Gyokeres was due back for pre-season training on July 12, after the club gave him permission to delay his return.
Arsenal have been in talks to sign the 27-year-old, but have so far failed to come to an agreement on a £69m deal.
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Varandas said: "We're calm. Everything can be solved with the closure of the market, a hefty fine and an apology to the group.
"If they don't want to pay Viktor's fair market value, we'll be very comfortable with that for the next three years.
"If the geniuses who are devising this strategy think that this puts pressure on me to make it easier for him to leave, not only are they completely wrong, but they are also making it more complicated for the player to leave.
"No one is above the interests of the club. Whoever they are."
Sporting are believed to want an initial fee of £60.4m, plus £8.6m in add-ons.
Sky Sports to show 215 live Premier League games from next season
From next season, Sky Sports' Premier League coverage will increase from 128 matches to at least 215 games exclusively live.
And 80 per cent of all televised Premier League games next season are on Sky Sports.