Mane has proved to be an excellent signing from Southampton, but will miss some January games because of Senegal's participation in the Africa Cup of Nations.
Molby thinks conceding goals can keep the Reds sharp.
Liverpool take on Manchester United on Monday night at Anfield, and there will be plenty of eyes on who will be starting in goal for the home side.
Klopp was appointed Liverpool manager a year ago on Saturday.
Premier League rivals Liverpool and Tottenham Hotspur will face each other in the EFL Cup next month.
Sakho was told to leave the club on loan, but remains at Liverpool now the transfer deadline has passed.
Molby says he had no problem with Daniel Sturridge's comments when asked about his role, and doesn't think Jurgen Klopp will either.
Liverpool will be hoping to get back to winning ways in the Premier League with a tough test against Tottenham after last weekend's defeat to Burnley.
Molby has made the bold comparison that Sadio Mane has had the same effect on Liverpool as John Barnes did when he first signed back in 1987.
Molby predicts Klopp will be bold when the Reds open up their Premier League campaign.