19-year-old Ter Stegen is currently regarded as one of the brightest prospects in German football after establishing himself as Gladbach's first choice goalkeeper, and made a couple of brilliant saves in his side's 3-1 win over Bayern on Friday evening.
On the other hand, Neuer, who many feel is the best goalkeeper in the world at the moment, made a howler in the 11th minute, clearing the ball straight to Marco Reus who capitalised to give Gladbach the lead.
And while that mistake is unlikely to tarnish the good start Neuer has made to his Bayern career since joining from Schalke last summer, Maier believes the 25-year-old needs to be wary of Ter Stegen's emergence.
"Marc is virtually on par with Manuel Neuer," Maier told Bild. "Neuer has just preceded him, he plays for Bayern and can distinguish himself internationally.
"[Ter Stegen] is now a great goalkeeper."
Ter Stegen has been called up to the Germany U-21 squad, but is yet to receive the nod from senior coach Joachim Low.