Eintracht Frankfurt have not revealed which club is involved, but Skhiri has been strongly linked with a return to 1. FC Koln in recent weeks. The 31-year-old, who is under contract until 2027, played for Cologne between 2019 and 2023 before moving to Frankfurt.
Meanwhile, new Frankfurt head coach Adi Hutter has also left three forwards out of the training camp squad, with Michy Batshuayi, 32, Noel Futkeu, 23, and Jessic Ngankam, 26, all having been placed on the club's transfer list for some time and occasionally training away from the main group.
By contrast, Junior Dina Ebimbe, 25, and Niels Nkounkou, 25, have both been included in the travelling party, in what was considered a mild surprise given their own uncertain situations at the club.
Skhiri returned to Frankfurt's pre-season preparations earlier this month following a disappointing World Cup campaign with Tunisia, who exited at the group stage after three bitterly disappointing defeats. His long-term role at the club had already been in question before the tournament, with his game time having declined last season and the signing of Noel Aseko from Bayern Munich pointing to the future at the base of Frankfurt's midfield.
Reports in Germany also suggest the club are working to add further experience in that area with a move for Bayer Leverkusen's Robert Andrich, leaving Skhiri's path back into regular contention increasingly narrow.
Koln, for their part, are said to value Skhiri's experience and ability to speed up their play, qualities head coach Rene Wagner - who worked as an assistant during Skhiri's first spell at the club - is understood to rate highly.
Since his free transfer to Frankfurt in 2023, Skhiri made 117 appearances for the club across all competitions, scoring seven goals and providing seven assists, and was a regular contributor to some of the side's most memorable European nights.
Any return to Koln would represent a significant reunion for a player who quickly became a fan favourite during his first spell at the club, when he established himself as one of the Bundesliga's most reliable defensive midfielders before his move to Frankfurt.