Poyet told the Sunderland Echo: "We have been trying to help a few players who were finding it difficult to get involved and Modibo is one of them.
"As of now, we have five senior centre halves on our training ground without him.
"We have that, because Carlos Cuellar has now returned to full training, so getting him involved was going to be even more difficult.
"And Modibo? He's the sort of player who needs to play.
"I think that Diakite has one thing which is important - he is very strong.
"He has a specialist strength and when you are like that, you need to be playing regularly to keep you at your maximum effectiveness.
"If Modibo is not playing, you are not going to get the best out of him.
"Others can be different - Santiago Vergini for example has a different type of fitness, you can always play him - but Modibo needs a run of games and we couldn't give him that.
"So the best thing for him was to go there to Fiorentina and hopefully get the run of games he needs."
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