Former Chelsea defender Frank Leboeuf has admitted that he is undecided regarding the club's signing of Demba Ba.

The Senegalese striker sealed his switch to Stamford Bridge from Newcastle United earlier today, having spent the past 48 hours in talks with Chelsea officials and undergoing a medical.

However, despite insisting that the Blues have a "bargain", World Cup winner Leboeuf believes that 27-year-old Ba will need to prove his "mental strength" before he can be classed as a success.

"First I think it is a bargain – especially for a player that has scored so many goals for Newcastle and has been their main player," the Frenchman told Sports Mole. "There are still some question marks though. How will he cope at a big club? Newcastle is a big club that are struggling right now to get results, but he will be between big stars at Chelsea.

"Whether Demba Ba will find his own room or not, I don't know. I know his quality and his motivation, but I don't know his mental strength. If he has all three, he will be successful at Chelsea. If psychologically he is going to be drawn in by the presence of other players, he's going to struggle."

Leboeuf has also said that Ba's arrival could have a negative impact on Fernando Torres, who has been Chelsea's main centre-forward this season following the summer departure of Didier Drogba.

"There has always been question marks over Torres's psychological aspects. We saw last year and the year before when competing against Didier Drogba it was a problem for him," the ESPN analyst added. "If Demba Ba starts scoring goals every time he plays, it's going to be a problem for Torres.

"For the good of Chelsea it would be good to see Ba and Torres scoring, but I don't think they can play as a pair so Rafael Benitez will have to make choices. Then we will see how they react."

Ba could make his Chelsea debut during tomorrow's FA Cup tie at Southampton.

ESPN will air live and exclusive coverage of three FA Cup Third Round games this weekend. Swansea City vs. Arsenal at 1pm and Mansfield Town vs. Liverpool at 3.45pm on Sunday, then Cheltenham vs. Everton at 7pm on Monday. Visit ESPN.co.uk/tv for details.