Newcastle's Ryan Taylor could miss the whole of next season after suffering a further cruciate knee ligament injury.
The defender first injured his knee in the Europa League win over Atromitos in August and had surgery soon after.
"Ryan has worked so hard and diligently," said Newcastle manager Alan Pardew. "Clearly everyone at the club is deeply saddened by this news."
Meanwhile, Magpies goalkeeper Tim Krul will have surgery on his dislocated shoulder on Monday.
The 25-year-old, who suffered the injury in the 3-0 defeat by Sunderland on Sunday, is expected to return to training at the end of July.
Taylor, 28, suffered the latest setback to his fitness following his recent return to training.
"Ryan has been a model patient and has given his all to ensure he could return to full training in the best condition possible," added Pardew. "Ryan has, and will continue to, receive the full support of everyone at Newcastle United during this difficult time for him."
Taylor joined Newcastle from Wigan in 2009 and has made 91 appearances for the club.