Rhodes, 54, had been back at the club for just four months before seeing his contract terminated.
He joined the coaching staff as Frankie Bunn was appointed first-team boss in June - the duo had played together at Oldham between 1988 and 1990.
Rhodes also worked with the 'Latics' as a goalkeeping coach in 2002.
Oldham sit 12th in League Two after 16 matches and face Northampton on Saturday.