Reacting to Liverpool's 1-1 draw at Champions League opponents Lyon, Souness was critical of Benitez's transfer policy.
"My criticism is what I've mentioned before. I think he's been there five years, and spent more money than anybody else other than Chelsea," Souness told Sky Sports.
"Injuries are part of the game especially when you get to November time. That's when they kick in generally. I think what's behind the first XI isn't good enough to go and win games like that [at Lyon].
"Now Lyon aren't a great team. Lyon won at Anfield then lost 4-1 at Nice in the next game they played.
"What I can tell you is that if Rafa had been at any other club, any other big club, whether it be Arsenal, Man United or Chelsea, he wouldn't be there because I don't think the supporters at those clubs are like Liverpool supporters.
"I think they [Liverpool fans] will be a bit more patient and give a manager a bit more time."