Werder Bremen have made an enquiry for Everton midfielder Davy Klaassen, according to Sky sources.
The former Ajax captain arrived at Goodison Park for £23.5m in June 2017 but was limited to just seven Premier League appearances last season as the Toffees endured major managerial changes.
Ronald Koeman signed the 25-year-old in June but he was dismissed in October and replaced by Sam Allardyce, who left in May this year, and has been succeeded by former Watford head coach Marco Silva for the new season.
Silva has told Sky Sports News that he expects departures after assessing his squad over pre-season with the Bundesliga club interested in the Dutchman.
Having made his debut for Ajax as an 18-year-old in 2011, Klaassen went on to make 163 appearances in total, scoring 49 goals and taking his side to the Europa League final in the 2016-17 season, before making a move to England.
In the other direction, Watford's Richarlison is expected to complete a £50m move to Everton having passed a medical on Monday.
The 21-year-old winger, who was signed by the Hornets last summer when Silva was in charge at Vicarage Road, returned home early from a pre-season training camp in Austria.
Richarlison joined Watford from Fluminense for £13m last August and impressed in his debut Premier League season, scoring five goals in his first 12 appearances.