Paris St Germain are confident they could sign Lionel Messi within a week, and expect to make money on signing the Argentinian superstar.

Barcelona have conceded they are unable to keep him, with club president Joan Laporta blaming the former regime at the club and LaLiga spending rules for thwarting any hope of Messi signing a new contract at the Nou Camp.

PSG were initially concerned about pursuing a deal on financial grounds when Barcelona announced on Thursday night that Messi was leaving, but sources close to the matter said the position changed when the club hierarchy learned of a call from Messi to PSG coach Mauricio Pochettino on Thursday.

That personal connection shifted the dynamic and led to PSG president Nasser Al Khelaifi asking the club’s commercial executives to carry out a fresh assessment on Thursday night and Friday morning of how the numbers would stack up if Messi was signed.

The result was a decision to go after Messi, on the basis that the deal would pay for itself via improved sponsorship, merchandising and even touring revenue.

The French side appear to be in pole position, especially so since Messi’s former Barcelona coach, Pep Guardiola, ruled out the possibility of Manchester City joining the race to sign him.

Pochettino, on the other hand, told the media on Friday afternoon that a deal for Messi “could happen”.

“When you talk about players of his stature I think that many clubs, and in this case Paris St Germain, these opportunities sometimes come up and sometimes they don’t,” he said.

“The club is working hard, as I said, and if there is any information we will let you know. In every case, we are evaluating the options and, of course, this is one of those.

“When we talk about the transfer window, it is obvious that this is something that could happen, but our responsibility as coaches is to make sure the players who are available tomorrow for the game against Troyes are focused on the game.”

Laporta held a media conference on Friday morning to discuss Messi’s departure.

He felt his leadership team had been left with a “terrible inheritance” from their predecessors, as he claimed club salaries were running at 110% of income when he took over.

He also said LaLiga’s strict squad wage-cap rules meant there was no way to do a deal. The club would stand to receive around £200 million instantly from the proposed sale of a 10% stake in LaLiga to private equity firm CVC Capital, which would give them the means to keep Messi.

However, Barcelona have rejected the proposed investment, with Laporta saying it would lead to the club “mortgaging their TV rights for half a century”.

It has been suggested by some observers that the Messi announcement was a tactical move by Barcelona to force LaLiga to back down on the wage-cap restrictions, and that a league without Messi would be unattractive to LaLiga’s would-be investors. But if this is brinkmanship from Laporta, then he really is taking it right to the edge.

Football finance expert Kieran Maguire believes although Barcelona’s hands are tied on Messi, there are clubs who can afford him and still comply with Financial Fair Play requirements.

Maguire, a senior teacher in accountancy at the University of Liverpool, told PA: “PSG are confident that he will be so popular with sponsors that the additional revenue that he will generate will offset the wage costs, so that would be one option.

“The other option is the MLS. While they have a wage cap, they have a designated player clause.”

Guardiola expressed his sadness that the Messi love affair with Barcelona was coming to an end, and said: “I would love him to finish [at Barcelona] but today the club’s sustainability is so important and what happened in the last year was really not good.

“I have incredible gratitude as a fan for the most extraordinary player I have seen in my life.

“I, of course, wish him the best for the last years of his career and he will not be forgotten, that’s for sure.”