Hoffer joins Frankfurt on loan

The Austria international, 25, spent last season on loan at the club as they won promotion to the Bundesliga.

He scored nine goals during that campaign, and had spent the previous campaign on loan at Kaiserslautern.

Hoffer joined Napoli from Rapid Vienna in 2009 but has struggled to make an impact in the first team, failing to score in eight Serie A appearances.

He has 28 caps for Austria, scoring four goals.