Diangana has been a revelation for the Baggies ever since arriving at The Hawthorns on a season-long loan deal back in August.
The winger has netted four times and registered six assists in 18 outings for Slaven Bilic’s side.
The Express & Star understands that form has led to senior figures at West Ham believing the 21-year-old should be recalled next month.
Pellegrini also faces pressure from some supporters to take Diangana back to the London Stadium.
The Chilean, though, has previously said it will be better for Diangana’s development to remain at The Hawthorns and play 40 games this year.
It is understood Pellegrini still believes that is the case with the 66-year-old strong enough to deal with any backlash from West Ham’s board or fans.
But with the Hammers having lost seven of their last nine games, it has been reported they will sack Pellegrini if they lose at Southampton tomorrow.
And should that happen, any new boss is sure to recall Diangana so they can make their own assessment of the player.
Albion have identified a number of players to replace the wideman if he does leave. And it is understood some of those targets are not left-wingers, with Bilic open to making tactical tweaks if a wide player of Diangana’s quality isn’t available.
As well as making an addition, the Baggies are also considering whether to recall Jonathan Leko from his loan at Charlton should Diangana depart.
Leko will then compete with Kyle Edwards for a place on the left wing if Bilic decides to play the 4-2-3-1 formation he has primarily used this season.