The Gunners are set to be without captain Martin Odegaard for a few weeks due to an ankle problem.
They will also be missing Declan Rice, who is serving a suspension against Tottenham in the North London derby this weekend.
Pires told Wettbasis.com: “It is certainly a bitter loss because Rice is the linchpin of this team and his vast experience means that opponents have great respect for him."
“Nevertheless, Arsenal can win this derby without him because the squad is better staffed.”
“William's development is absolutely top-notch," said Pires on defender William Saliba.
"I am particularly impressed by his positioning. He hardly ever makes bad passes and never makes unnecessary fouls, which is a top quality. He has become incredibly consistent and fast.
“He is currently one of the best center-backs in the Premier League."