Arsenal forward Joel Campbell is to move in the opposite direction as part of the deal, with the Costa Rica international set to see out the season on loan in Spain.
No financial details have been released, but Sky Sports have been among those to suggest that any deal hinged on a £15 million buy-out clause being met.
Whatever the terms may be, Marcelino concedes that they make sound business and career sense for those at the centre of the talks.
He said in AS: “Gabriel’s departure surprised us all because we didn’t expect to make changes to the squad. From a sporting point of view it’s unfortunate, but neither the club nor the player could afford to resist Arsenal’s offer. I wish him the greatest professional success.
“We’ll now seek a new centre-back. We have the resources to replace Gabriel, but finding a replacement won’t be easy because the level of demand is increasing.
“[Joel Campbell] is an interesting signing for Villarreal because he can play several positions and has a different profile to the players we already have.”
Paulista is yet to represent Brazil at any level, so the completion of any deal with Arsenal rests on a successful work permit application.
Villarreal would appear to consider that a formality, with attention already turning to possible replacements.
Arsene Wenger will be hoping that the relevant paperwork is processed without a hitch, as he was expected to move for defensive reinforcements during the January transfer window.