The 19-year-old was named in Joachim Low's provisional 30-man squad for the FIFA World Cup but was cut from the party along with clubmate Max Meyer.
His inclusion in the squad came after a solid debut season at the Veltins Arena where he made 32 appearances in all competitions.
The former Bochum man helped Schalke to a third-placed finish in the Bundesliga, but Gerland feels the promising German should focus on playing for clubs of Bayern's calibre.
"Goretzka is of the level to play at Bayern Munich," RevierSport quotes him as saying.
"Now he has signed a long-term contract at Schalke, but if you're as good as he is, he must also play for Bayern during his career."
Goretzka reportedly turned down interest from Borussia Dortmund prior to signing for their rivals Schalke in July last year.
Prior to his move, he had been a key figure for hometown team Bochum in the 2. Bundesliga.
