Claudio Ranieri recklessly gambled with Chelsea's Champions League hopes in Monte Carlo and lost heavily in a defeat which may prove the final straw for his impatient boss, Roman Abramovich.

There is, of course, still some hope for Chelsea in the second leg of their Champions League semi-final against Monaco back at Stamford Bridge in a fortnight's time.

However, this was a tie there for the taking when Monaco, who had been pegged back to 1-1 by Hernan Crespo keeping his promise to deliver, were reduced to 10 men with 37 minutes left.

It was not even a warranted dismissal as Claude Makelele seemed to be guilty of - not to put too fine a point on it - blatant play-acting in making the most of the weakest of pushes.

Ranieri clearly sensed blood and sent on Jimmy Floyd Hasselbaink in a three-pronged strikeforce, while Mario Melchiot was replaced at right-back by first a midfielder - Scott Parker - and then a centre-back, Robert Huth.

They were quixotic moves but no more so than usual. Then again, this time the Italian's tinkering was fully punished. The blood may yet prove, metaphorically at least, to be Ranieri's own.

For as Chelsea naively pushed forward, they left themselves open at the back and first Fernando Morientes, on loan from Real Madrid, and then Shabani Nonda took full advantage.

And so Chelsea had put themselves on the precipice of elimination from the apparent brink of success, all in front of a Russian multi-millionaire who simply does not tolerate failure.

Marcel Desailly, meanwhile, also escaped with an apparent elbow on Morientes that could still bring him post-match punishment.

Chelsea now need to win 2-0 at Stamford Bridge to make it through to the final and, while hope is not altogether lost, their recent record at home is none too impressive.

Indeed, they have stumbled ever since their quarter-final victory against Arsenal, with goalless draws against both Middlesbrough and Everton at home.

They made another unconvincing start in the Louis II stadium, with Monaco seizing the lead after just 16 minutes.

Melchiot was late with a tackle on Jerome Rothen and the winger exacted full punishment as he swung over the free-kick from which Monaco seized the lead.

Crespo tried to clear but the ball instead carried to the far post, where Prso sent a looping header past Marco Ambrosio into the far corner.

Chelsea took just five minutes to respond as Frank Lampard delivered an incisive cross which found three team-mates unmarked after - perhaps questionably - beating the offside trap.

Parker and Eidur Gudjohnsen combined to scramble the ball sideways to the lurking figure of Crespo, who pounced as he turned and beat 'keeper Flavio Roma from point-blank range.

Now Chelsea were fully re-energised as Lampard shot wide and then crossed for Crespo to stab the ball over the bar.

Ranieri's side still had to be cautious, with their defence remaining uncertain and the dangerous Ludovic Giuly beating Terry for pace before forcing Ambrosio into a neat save at the near post.

Lampard was at least orchestrating Chelsea's midfield with assurance and poise, but the danger remained as Gael Givet headed just over the bar.

Ranieri cannot resist a half-time change, however, and the ineffective Jesper Gronkjaer was replaced by Juan Sebastian Veron.

That, however, only succeeded in inviting Monaco to attack, with Ambrosio beating away Prso's header, while Marcel Desailly cleared off the line from Morientes.

Then came the moment that should have stacked the odds in Chelsea's favour, when Andreas Zikos went down under a challenge from Makelele and responded by pushing the Frenchman away.

Makelele completely over-reacted and dived to the ground in supposed pain, clutching his head, and referee Urs Meier caused uproar among the home fans by sending the Monaco midfielder off.

While Monaco hastily re-organised, Ranieri indulged in a frantic spell of tinkering as he upped the ante in bringing on Hasselbaink and taking off first Melchiot and then Parker.

Gudjohnsen twice came close, while Hasselbaink and Huth also threatened, but Chelsea had over-extended themselves.

First Morientes strode clear and buried his shot past Ambrosio and then, with seven minutes left, the stand-in Chelsea keeper was all too easily beaten by Nonda as well.

The gamble had been lost. Ranieri and his side can still redeem themselves in the return fixture but the Italian's future has never seemed more uncertain.

Teams

Monaco: Roma, Evra, Ibarra, Bernardi, Giuly (Nonda 83), Prso (Cisse 57), Morientes, Zikos, Rothen (Plasil 89), Rodriguez, Givet.

Subs Not Used: Sylva, Oshadogan, Adebayor, El Fakiri.

Sent Off: Zikos (53).

Booked: Ibarra.

Goals: Prso 17, Morientes 78, Nonda 83.

Chelsea: Ambrosio, Makelele, Desailly, Lampard, Melchiot (Hasselbaink 62), Bridge, Parker (Huth 69), Crespo, Gudjohnsen, Terry, Gronkjaer (Veron 46).

Subs Not Used: Sullivan, Mutu, Cole, Geremi.

Booked: Melchiot, Makelele, Terry.

Goals: Crespo 22.

Att: 15,000

Ref: Urs Meier (Switzerland).