The free transfer from Chelsea has struggled with form and injury since his summer arrival.
However, Arteta isn't writing off the Brazil international and remains confident he can help William get back to his best.
And just as a reminder to Gooners of what Willian is capable of, we have one of the best moments from the Brazilian for former club Corinthians. It was 14 years ago when a teenage Willian scored a spectacular double for Corinthians in their 2-2 draw with Athletico-PR - a performance which announced him to scouts across Europe.
Watch below (and for more videos click here):