Boro sealed a 1-0 win over the Premier League side in the first leg of their semi-final clash on Tuesday night.
Hayden Hackney scored the game’s only goal with Chelsea missing a number of chances against the Championship side.
Former Blues defender Leboeuf was left hugely frustrated with another underwhelming performance from his own side, accusing them of adopting an unnecessary risk-averse approach.
The former France international also lamented Mauricio Pochettino’s players for ‘not knowing what to do with the ball’ – singling out 21-year-old Madueke for particularly scathing criticism.
Leboeuf pinpointed incidents where the England Under-21 international put crosses into the Middlesbrough box with no teammates in sights, remarking ‘the last time I saw that I was 14 years old in my village’.
‘They don’t know how to across the ball, they don’t know how to play one-twos or with pace in the game, when they have some chances to go or it, they go back,’ Leboeuf told ESPN.
‘It is like the coach told me to not lose the ball and not risk anything, maybe it’s that. Madueke at one point, he made the cross where we could see there was no Chelsea player in the 16-yard box. But he made it.
‘The last time I saw that I was 14 years old in my village where you don’t know what to do with the ball so you cross it and you don’t care about it.
‘The guy is a professional player, it means he crossed by instinct, he doesn’t know what he does, he does not inform himself on what he has to do. That is absolutely appalling.
‘It’s not just him, they are all the same. It is amazing.’
Chelsea will have the chance to rescue the semi-final tie when they host Michael Carrick’s side at Stamford Bridge on Tuesday 23 January.
Before then, they host Fulham in a west London derby on Saturday afternoon.
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