Chelsea produced a professional performance to beat FC Porto 2-0 in the away leg of their Champions League quarter-final tie on Wednesday night.
The result means Chelsea are now firm favourites to go through to the semi-finals of the competition and are being considered one of the clubs who could go all the way in the Champions League this season.
Leboeuf cautioned against any complacency in the Chelsea team ahead of the next leg and insisted that the club are yet to solve their problems up front despite the result against Porto.
He believes only Mount is guaranteed to play every game for Chelsea at the moment due to his form but feels every other player in the team has question marks hanging over their head.
Leboeuf said on ESPN FC: “The job is not done, you still have the return [leg].
“Chelsea still have problems up front. They keep on winning except last week but they still have a problem.
“There is one thing that we are sure of is that Mason Mount should play every game because that guy makes a difference.
“Otherwise, for the others, question marks over all of them.”
Chelsea will look to bounce back in the league on Saturday when they will take on Crystal Palace at Selhurst Park.