Andre Villas-Boas' bid to rescue Chelsea's season is being sabotaged by Jose Mourinho's continued contact with his former players, according to the estranged duo's old boss.

Porto president Jorge Nuno Pinto da Costa, who gave both Mourinho and Villas-Boas their big breaks in management, claimed the latter could not succeed at Stamford Bridge unless Mourinho cut all ties with the squad.

Pinto da Costa also suggested Roman Abramovich was aware Villas-Boas' authority was being undermined by the spectre of Mourinho, who worked with many of the players still at Chelsea today.

Billionaire owner Abramovich has given Villas-Boas - who assisted Mourinho for several years before forging his own managerial career - the green light to replace those players, but it is proving a turbulent transition.

Abramovich reportedly saw the 34-year-old openly challenged by some of his squad during frank exchanges at the club's training ground on Sunday after they slumped to fifth in the Barclays Premier League.

That has increased speculation over Villas-Boas' position but Pinto da Costa told La Gazzetta dello Sport: "He will be successful with Chelsea because his contract isn't just for one year.

"He needs time to mould his own team and he can't do that as long as there are players, as I've heard, who exchange text messages with Mourinho.

"And Abramovich knows this."

Despite Villas-Boas' record as Chelsea boss being worse than any of his predecessors during the Abramovich era, the club have repeatedly insisted his job is not on the line.

Pinto da Costa said: "The only thing that will topple Villas-Boas is if he fails to qualify for the Champions League."

And the Porto president insisted getting the bullet would not taint Villas-Boas' future prospects, claiming he would walk into the Inter Milan job if it became available.

He said: "If he leaves Chelsea, he'll be the next coach of Inter."

One man who will not be adding to the pressure on Villas-Boas is Guus Hiddink, whose agent today insisted the Dutchman would not reveal whether he would answer another SOS from Abramovich while the Chelsea hotseat was still occupied.

Hiddink famously rescued the Blues' faltering campaign three years ago following the sacking of Luiz Felipe Scolari and has remained in contact with Abramovich.

But the pair have not spoken since the end of last year, according to Hiddink's representative, who said the 65-year-old was mulling over a number of offers to return to the game having been a free agent since October.

Cees van Nieuwenhuizen told Press Association Sport: "He has offers on the table, obviously, but he is not in a hurry and he is making up his mind."

He added of Chelsea: "I know they are not doing too well at the moment, but Guus never puts himself in a position that he says he is interested in whatever job if there is still coach who is doing the job.

"For him, that's not the way to treat your colleagues."

Hiddink has also been linked with the England job following Fabio Capello's shock resignation last week but Van Nieuwenhuizen all but ruled out his client succeeding the Italian.

The Football Association would not allow the new manager to pick John Terry as captain pending the outcome of his racism trial, something that would put Hiddink in a difficult position considering his relationship with the Chelsea star.

"I think the England job is not a serious option because of his personal relationship with John Terry," Van Nieuwenhuizen said.

Anzhi Makhachkala were strongly touted as another option for Hiddink towards the end of last year.

The mega-rich Ukrainians instead appointed Yuri Krasnozhan, who lasted barely a month before losing his job yesterday.

Van Nieuwenhuizen said: "I understood that Capello is talking to them.

"Anzhi was an option around the holidays in December and they decided to take the Russian guy, who is now out."