The 30-year-old has been at Schalke since 2013, and gives Watford another defensive option to consider.
The Baggies have been linked with a move for the Leeds left-back Charlie Taylor.
The former German international would be a canny addition for Leeds United if they earn promotion.
Sunderland are believed to be interested in the versatile German.
Left-back Dennis Aogo, who was being touted as a potential Anfield addition in January, will move permanently to Gelsenkirchen.
Will Schalke sign Liverpool target Dennis Aogo despite his knee injury? – Quite likely after what general manager Heldt said.
Liverpool target Dennis Aogo has suffered a cruel blow.
A former German international was killed as a terrorist in Syria last month, it has been revealed.
Liverpool have been linked with signing Dennis Aogo.
Dennis Aogo of Hamburg is a much better long term replacement for Patrice Evra at Manchester United than Leighton Baines.
Liverpool defender Dejan Lovren has played an important role for Jurgen Klopp's side in recent weeks.
Tottenham Hotspur have been linked with a strange move for Nemanja Matic.
Tottenham Hotspur defender Jan Vertonghen is set to miss out on featuring against West Ham United.
The summer Rangers recruit has been absent since Steven Gerrard's side lost the season's first Old Firm at Ibrox.
Matej Vydra hasn't started a Premier League game for Sean Dyche all season but he could drag Leeds United to the Championship title.
Tottenham Hotspur are reportedly keen on Benfica's Ruben Dias.
Soumare is one of Ligue 1's best midfielders and he could be about to become Mourinho's first signing since his return to the Premier League with Spurs.
Tottenham Hotspur defender Japhet Tanganga enjoyed a wonderful pre-season, but has rarely been used this term.
The latest reports suggest that Chelsea winger Christian Pulisic will miss out on playing against Manchester City this weekend.
Tottenham Hotspur boss Mauricio Pochettino has now been replaced by Jose Mourinho.