Arsenal have confirmed Shkodran Mustafi’s departure to Schalke as Ainsley Maitland-Niles has joined West Brom on loan.
The Germany defender has agreed to cancel the last six months of his Gunners contract to secure a move back to his homeland.
Arsenal boss Mikel Arteta said: “Musti has been a key player for us for a long period of time.
“He played a very important part in my first season as manager and I’d like to thank him for his professionalism and for always being ready when called upon.
“Everybody at Arsenal wishes Musti well at Schalke.”
Arsenal technical director Edu added: “We thank Musti for his contribution at Arsenal which has spanned four-and-a-half years, more than 150 appearances and a prominent role in two FA Cup wins.
“Everyone associated with the club wishes Musti and his family the very best wishes for the next chapter in his career.”
Mustafi, who signed for Arsenal in a £35million deal from Valencia in 2016, has made just nine appearances under Mikel Arteta this season.
Elsewhere, West Brom have brought in Arsenal midfielder Maitland-Niles on loan until the end of the season.
Leicester and Southampton were also in for the England international, who can operate in midfield or defence, but West Brom have won the race for his signature with Maitland-Niles.
The 23-year-old will be looking to aid the Baggies’ survival hopes with Sam Allardyce’s side nine points from safety.
Arteta said: “Ainsley is a very talented player and we are proud of his hard work and development with us.
“This decision to go on loan to West Bromwich Albion for the rest of this season is to support Ainsley and his growth further.
“He will be working at a very good club in the Premier League and we all wish him the best of luck during his time at the Hawthorns.”