Cascarino, who played in the Premier League for Chelsea, believes the German needs to fix up on his leadership skills at the back.
"The one position I'm a little bit concerned about with Arsenal, and it worried me watching them last season, is the keeper," he said.
“I think Leno is a big player for them this year, he's got to be better.
“Last season, he was punching balls that were quite easily catchable,
“I was thinking, 'Wow, you've got to be better than that, you've got to be more commanding'."