Why Friday is AWOL Sunderland flop Didier Ndong's last chance of a big European move

The midfielder remains AWOL having failed to report for pre-season training at the Academy of Light, and has told the club that he wishes to leave.

Ndong came close to an exit during the summer but no deal was finalised before the August 31 deadline leaving the Gabon international in a state of limbo.

LIVE: The latest from the Stadium of Light - with big injury updatesOne club linked with a move for the midfielder were Benfica, and they could still revive their interest in the next few days.

With the Portuguese window remaining open for a few more days, an exit could still be sealed - but must be done so by the of this week.

Here's everything you need to know as Ndong pursues a last-ditch move away:

When does the Portuguese transfer window close?

While the majority of Europe saw their transfer windows close on August 31, the Portuguese window runs for almost a month longer.

READ: Sunderland have the talent to cope without Charlie WykeHaving only opened in early July, clubs in Portugal are allowed to seal deals up to Friday, September 21.

This means clubs have another four days to finalise incoming and outgoing transfers before their window slams shut.

Clubs then have to wait until February 2 to sign players again - meaning they could be keen to seal those last-minute deals before this Friday's deadline.

Do Benfica need a central midfielder like Ndong?

The European giants were heavily-linked with Ndong earlier this summer, with a bid of €5.5m thought to be likely - although nothing came to fruition before England's transfer window closed.

According to reports in Portugal, via A Bola, this is because Benfica were instead pursuing a deal for ex-Chelsea midfielder Ramires.

But with that deal having failed to come off, they could well turn their attentions back to Ndong.

MORE: Jack Ross on tactical awareness, forward improvement and preparing for the oppositionThere is also uncertainty over the future of star midfielder Pizzi - who is thought to be interesting Wolves - so could boss Rui Vitoria be in the market for a preemptive replacement?

Is there any other interest in him?

There were several other clubs linked with Ndong over the summer months although, again, no deals came to fruition.

Torino were interested and managed to agree a fee with Sunderland, only for the player and his representatives demands to cause the deal to collapse.

Spanish side Leganes also harboured an interest towards the end of the window, but didn't reach the advanced stage that their Italian counterparts did.

What's Sunderland's stance on the matter?

With Ndong still yet to return to the club, Sunderland are withholding the midfielder's wages - while legal proceedings have already been opened against fellow wantaway Papy Djilobodji, who has been served notice of the termination of his contract.

LIVE: Injury latest from Sunderland with updates on Wyke and McGeouchManager Jack Ross is hopeful a solution can be found, and doesn't envisage either player forming part of his first team squad.

“They may do [return] and if they do we’ll deal with them accordingly when they come in,” he said.

“I haven’t had any interest in them because they’ve never turned up and haven’t been part of what I’ve tried to build here. I don’t ever envisage them being part of that.