Old acquaintance who poses greatest threat to Chelsea's ambitions

Chelsea can but hope that the "hex of the ex" is not functioning when they face Didier Deschamps' Monaco in the Champions' League semi-finals.

That immutable law - which states that former players return to haunt you - was illustrated in spectacular fashion on Tuesday when Fernando Morientes, on loan at Monaco from Real Madrid, helped to seal Real's exit from Europe's top table. The Spanish striker scored with a brilliant header in the 3-1 win, a scoreline that was sufficient for victory on the away goals rule in a quarter-final tie that ended 5-5 on aggregate. Morientes had also scored in the 4-2 first-leg defeat in the Bernabeu.

Though Deschamps' role as a player was unfairly disparaged by Eric Cantona as that of "water carrier", there has been little prosaic about the former Chelsea midfielder's fledgling managerial career. At Monaco, he has not so much carried water as turned it into wine.

The single best decision in his two-year reign at Stade Louis II was made on 31 August last year. It was on that summer Sunday that he sealed the deal to take Morientes on loan for the season. Morientes had just watched Monaco beat Metz to go top of the French First Division, where they remain. "I wish to help them stay at the top of the standings, they're a good team and I'm full of hope," the striker said at the time. Even before Tuesday's astonishing success, his hopes had been realised. He credited Deschamps for making that happen. "I'll never forget that Monaco gave me the chance and joy to play again after a year of suffering," he said.

Deschamps' masterstroke was not only to hire a player who had become marginalised by Ronaldo in Madrid but to forge a team in which he could prosper. The signs that he was succeeding arrived as early as last September, in Monaco's second group match in the Champions' League. They thrashed AEK Athens 4-0 to move to the top of Group C, with Morientes scoring twice.

That match also exemplified the strengths of Deschamps' youthful team. The key wide men, Jérôme Rothen and Ludovic Giuly, both shone, providing ammunition from the flanks. Morientes used his aerial power to pressure AEK's defence all night. Giuly, the club captain who is at his best when roaming inside, also scored.

Deschamps reacted with the kind of calm that characterised his playing days, preferring to shrug at the display rather than hype it up. "Against a better team it would have been a lot more difficult," he said. By the time Monaco had progressed to the knock-out stages, demolishing Deportivo 8-3 in a Champions' League record win along the way, he was only slightly more effusive. "It's a reward for all the hard work my players put in, day in and day out," he said.

Resilience as well as flair was required in the last 16 to move past Lokomotiv Moscow 2-2 on aggregate after a first-leg defeat. So to Real Madrid, who on Tuesday seemed out of sight at 1-0 up (and 5-2 on aggregate) before Monaco's stirring comeback. At last Deschamps felt comfortable enough to enthuse: "It was quite simply an extraordinary performance from my team. They went beyond their limits, both physically and mentally."

For all Cantona's criticism, Deschamps pushed himself to his own limits in a trophy-laden playing career with Nantes, Marseilles, Bordeaux, Juventus, Chelsea and Valencia. His successes at club level included Champions' League wins with Marseilles and Juventus, league titles in France (twice) and Italy (three times), and an FA Cup win with Chelsea.

Deschamps also held the record for the number of France caps (103) until he was overtaken by his good friend Marcel Desailly, whom he has played alongside at four different clubs as well as internationally. As a winner at the 1998 World Cup (as captain) and at Euro 2000, he did it all at international level.

"Fate forced me to play against friends," Morientes said after eliminating Real. Now it is Deschamps' turn. He said yesterday: "It will be a special evening when I go back to Stamford Bridge because I still have a lot of friends there." Yet it would not be surprising if he also felt he had unfinished business.

After being lured to London in 1999 by his friend Gianluca Vialli, he stayed only one season but his sojourn saw some historic occasions. These included being a member of the first all-foreign side to play in the English League (in Chelsea's Premiership match with Southampton on Boxing Day 1999) and being an FA Cup -winner in Wembley's last final (in 2000). But the year damaged his friendship with Vialli and was ultimately anti-climactic.

Losing to Chelsea now would be much worse. "We have no reason to fear them," Deschamps said. Chelsea should not think likewise.