Liverpool's Xabi Alonso will be out of action for three months with the broken ankle he suffered in the Reds' 1-0 defeat against Chelsea.
Alonso was initially expected to be out for six weeks after falling victim to Frank Lampard's robust challenge.
But the 23-year-old now faces a longer spell on the sidelines after learning he needs an operation to insert a screw into his left ankle.
The influential midfielder will undergo surgery on Thursday.
Alonso has become a key figure since his summer signing from Sociedad.
The playmaker joined Anfield in a £10.5m move and has made 23 appearances for Liverpool, scoring two goals.
Alonso joined Harry Kewell (groin), Milan Baros (hamstring) and long-term injury victims Vladimir Smicer (knee) and Djibril Cisse (broken leg) on the Anfield injury-list.
But Benitez would not be drawn on whether he would seek to bolster his squad in January's transfer window.
"We will see," Benitez said. "We have a good squad so we have players who can come into midfield."