The Morocco international striker is due to finalise his free-transfer move to the Emirates Stadium from Bordeaux in the coming weeks and Sagna has backed the 26-year-old to be a hit in the Premier League.
"He's a good player," the former Auxerre right-back told Sky Sports.
"I know him from France because I played against him many times and he has skills and is very good in the box so it will be good for Arsenal to have him and to play with him."
The France international added: "He will improve our training first and then on the pitch. He will need power and to fight more because English football is totally different from French football.
"But I'm not worried because I know he's a hard fighter."