Regular left-back Ashley Cole is out with a broken ankle while Russian deputy Yuri Zhirkov limped off in Saturday's 2-0 win at Wolverhampton Wanderers and defender Paulo Ferreira is not on their Champions League squad list.
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"We have problems because we are without two good players," former AC Milan coach Ancelotti told a news conference at his old San Siro haunt.
"We have Belletti who can play on the left ... he has been out (injured) for a while but has been training well all week. We will find a solution even if the absence of Cole and Zhirkov will hurt us."
Another option for Ancelotti could be to play left-sided midfielder Florent Malouda in defence.
Inter's Jose Mourinho, the former Chelsea coach, also has left-backs Davide Santon and Cristian Chivu injured.
He had been expected to pick captain Javier Zanetti on the left of the defence but said there was a chance he would play centre-half Ivan Cordoba there so that Zanetti could rampage through the midfield.
Doubts also remained over the fitness of Inter goalkeeper Julio Cesar, who missed training on Monday because of a car crash but practised on Tuesday.
"I'm not sure if he will play," said Mourinho. "I don't know how he will wake up tomorrow.
"After a car accident you don't know how the body reacts 24 hours or whatever later."
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