Andre-Pierre Gignac was at the double as Marseille ended their long wait for a Ligue 1 win with a 2-0 victory at struggling Metz on Friday.
Marcelo Bielsa's side were firmly in the running for the title not so long ago, but a dreadful run of four straight defeats put them in danger of missing out on Europe.
Gignac's 19th Ligue 1 goal of the season - and the 100th of his career in the French top flight - arrived seven minutes before the break.
Andre Ayew almost doubled Marseille's advantage soon after half-time, but Mezui made an outstanding save from his point-blank volley.
But there was nothing Mezui could do when faced with Gignac one-on-one in the 62nd minute, as the France international produced a classy dink over the home keeper to secure a much-needed three points for Bielsa.
