On Gnabry, Baggies boss Tony Pulis said in October 2015: 'Serge has come here to play games but he just hasn't been for me, at the moment, at that level to play the games'.
He was fresh from a starring role in Germany's silver-medal winning Olympic campaign, where he finished joint top scorer with Nils Petersen on six goals.
Gnabry became Bayern's fourth signing of the season after they permanent Kingsley Coman's deal and signed Hoffenheim stars Niklas Sule and Sebastian Rudy.
But those performances alerted Bayern to the 21-year-old winger's undoubtable talent and the Munich giants have not delayed in activating a clause in the youngster's contract.
The forthcoming summer transfer market could bring another move for Serge Gnabry, however, as the young Germany global is likely to be immediately loaned out of Bayern Munich, according to reports from German media outlet Kicker. "I am very happy as I am looking forward to an exciting time", Gnabry told the club's official homepage.
Filbry also said Bremen would not stand to make a profit from selling Gnabry.
Gnabry earned his first senior cap last November, scoring a hat-trick in the World Cup qualifier away to San Marino, which Germany won 8-0.