Dirar's side are preparing to embark on a UEFA Champions League quarter-final against Juventus starting Tuesday, while Monaco remain in the hunt for the French top flight title too.
Meanwhile, Falcao - on loan at Manchester United - looks set to go trophy-less in his first season at Old Trafford.
"We talk all the time with Falcao and James, but there was also Mounir [Obbadi] and Manu [Riviere] who left. All these players we have missed. Early in the season, we took a slap, it was hard," Dirar told Le Parisien.
"I think Falcao must be biting his fingers [ruing the fact] he's gone. Here, he would have played and participated in the Champions League. But he may need more atmosphere.
"In Monaco, he was not feeling well."
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