Slot is yet to see his first signing arrive since taking charge at the beginning of preseason.
Souness told the Three Up Front podcast: “I think Arne Slot still needs to strengthen in certain areas because if (Jurgen) Klopp couldn’t do it with the same group of players, then are they going to finish any better than third? I don’t think so," he said.
“Last season I thought the next manager after Klopp was walking into the dream situation, I don’t think it’s as dreamy anymore. They didn’t put their foot to the floor last season when it really mattered and they had a Premier League title to win with 10 games to go.
"The job is still great and Slot will walk into a dressing room full of energy with life in it, but it’s not quite as dreamy as it was.”