The 24-year-old did not take part in the club’s 6-0 Carabao Cup win over Barrow on Tuesday, and is expected to complete the transfer within 24 hours.
Wesley, who joined Villa from Bruges in a then club-record £21m deal two years ago, has been limited to just four substitute matches since recovering from a serious knee injury that kept him on the sidelines for nearly 16 months.
Villa hopes that returning to Belgium, where he previously spent three seasons, will reignite the Brazilian’s career.
With Wesley absent, young striker Cameron Archer scored a hat-trick as Villa comfortably qualified for the third round of the Carabao Cup.
Anwar El Ghazi also scored twice, including a Panenka penalty, as Frederick Gilbert netted the net in his first Villa appearance in nearly 12 months.
“When you have a little boy who goes in and scores a hat-trick, it’s always fun,” said Villa assistant coach Craig Shakespeare.
“I was very pleased to see the youth team last season. We had some young players training with us this season and they are making a claim.
“It wasn’t an easy match 6-0 and we have to give Barrow some credit. But Cameron was pleased to score a hat-trick.
“We have a strong squad and everyone knows we have some good young players. To help their development, it is important that they get opportunities like this. It is not just silk football, it is about developing a winning mentality.”