The former AC Milan and Paris Saint-Germain striker was appointed in September some three months before Dmitri Rybolovlev, who is 100th on the Forbes billionaires ranking with a $9 billion fortune, bought the principality club.
The 2004 Champions League finalists, who suffered a shock relegation in the 2010/11 season, spent millions on players during the January transfer window but could finish only eighth in the second division.
"We now wish to give the team fresh impetus for next season by bringing in experienced people to strengthen our coaching team," Rybolovlev was quoted as saying on the club website.
"The club should now be fully focused on... restoring the team to its rightful high position in the French football championship."
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