The Mexico international has looked certain to leave the Hammers permanently for the past 12 months, ever since his he was allowed to leave for Fenerbahce on loan last summer.
His time in Turkey was a frustrating one, with injuries preventing him from having a big enough impact for his move to be made permanent.

His return to Rush Green this summer had led to speculation that Nuno Espirito Santo might consider trying to convince him to stay.
But it appears the 28-year-old is set on leaving England altogether, with a move somewhere else on the continent preferred.
Alvarez was signed from Ajax to replace Declan Rice in 2024 and was a permanent fixture in David Moyes’ midfield, putting in some impressive performances during his maiden Premier League campaign.
But Moyes’ exit led to a change in tactical approach from his successors, Julen Lopetegui and Graham Potter.
That led to a drop-off in form before eventually falling out of favour altogether, hence his loan exit 12 months ago.
The Moyes favourite struggled to adapt to the systems Lopetegui and Potter wanted to implement and his future in east London has been questioned ever since.
Ajax considering Edson Alvarez return
According to De Telegraaf, the Eredivise giants are keen on bringing the defensive midfielder back to the Johan Cruyff Arena.
It’s claimed Alvarez would consider a return to Amsterdam, having already held positive discussions with club director Jordi Cruyff.
Indeed, at this stage West Ham want to cut ties with Alvarez and have asked for €15m (£12.8m).
However, it’s claimed Ajax are looking to sign the midfielder by raising funds through player sales instead of using West Ham’s final instalment as a possible bargaining chip in the deal.
That allegedly makes a deal complicated because Ajax aren’t currently close to selling any players and they’re unwilling to meet West Ham’s demands before that happens.
Ajax face competition for Edson Alvarez’s signature
Real Sociedad are also keen on Edson Alvarez but are looking at very different way to structure a possible deal.
It’s claimed they’ve proposed to buy 50% of Alvarez’s rights for €7.5m (£6.4m), with the rest paid via bonuses and add-ons.
Ajaz are also reportedly considering this approach, as well as a loan, but that would prove to be difficult given West Ham only want an outright sale.
The good news is, West Ham have two very interested parties and while it’s claimed Alvarez wants a return to Ajax, it could lead to negotiations that eventually drive the price up.
What’s almost certain is Alvarez’s time at West Ham is coming to an end.