Osasuna coach Jose Luis Mendilibar believes Real Madrid are getting back to their best ahead of the La Liga clash between the teams.
Inter president Massimo Moratti revealed this week the Serie A side had accepted the Istanbul side's offer, and several reports from Turkey on Saturday claimed the transfer was a done deal.
The Turkish Super Lig champions insisted they are yet to agree terms with the 28-year-old, but said talks were continuing.
"The transfer of Wesley Sneijder has been agreed between Inter and the club and negotiations are ongoing with the player," a statement on the club's website read.
"This has been brought to the attention to the public."
Sneijder was frozen out at the San Siro side over a contract dispute, and has not played since September.
The midfielder's agent said on Friday Sneijder will consider incoming offers in the next few weeks before making a final decision on his future.