Leno insists he has the tools to deliver as he revealed he has impressed the squad with his left foot and ability in one-on-one situations.
"His left foot is unbelievable," Leno told football.london. "Also his one-against-one against defenders is unbelievable.
"When he has space, he can be a key player for us in transition. I think and I'm sure that we'll have a lot of fun with him."
He has backed Pepe to show his match-winning exploits at West Ham can be a turning point and kick-start his Arsenal career.
Leno added: "Is it a turning point? I hope so. It was a hard time for him.
"But I think that's normal when you come to the Premier League."