Fiorentina coach Vincenzo Montella admits Micah Richards is on the outer.
Richards is on a season-long loan from Manchester City.
"He is more of a full-back in a four-man defence and when he arrived, in my view, his fitness levels weren't up to scratch to sustain that role," said Montella.
"Then we changed tactical system to 3-5-2 and compared to the others he is less prepared for this approach.
"He needs to work on it and be open to learning, which he is, but we must remember all decisions are made for the good of the team overall.
"He is certainly a player more suited to a four-man defence than three, in my view."