The 22-year-old has been suffering with tendinitis in both knees, and an operation is the only way to cure the problem. Mellor will join fellow forwards Djibril Cissé (broken leg) and Florent Sinama-Pongolle (knee) on the long-term casualty list at Anfield. Midfield player Xabi Alonso and goalkeeper Chris Kirkland are also unlikely to figure again in the current campaign with ankle and back injuries respectively.
Mellor only broke into the first-team picture at Liverpool this season, scoring five goals in 16 games. His strikes have included a last-minute winner in a 2-1 Premiership victory against Arsenal FC in November and a crucial goal the following month in the 3-1 win against UEFA Champions League group stage rivals Olympiacos CFP.
Mellor's absence means Liverpool go into next week's Champions League first knockout round return at Bayer 04 Leverkusen with only one recognised striker in Milan Baroš, as Fernando Morientes is cup-tied. The Premiership side have a 3-1 advantage from the first leg.
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