Sarr is high on the shopping list of Arsenal chief Sven Mislintat.
Having seen the youngster inspire Rennes into the final 32 of the Europa League, Sagnol enthused: "The star of this team is Ismaïla Sarr, there's nobody else.
"It is he who carries it offensively. He is consistent in his performances, his efforts.
"He is the only one since the beginning of the season who brings a real satisfaction."