The former Manchester United and Everton boss insists his squad possesses the depth to juggle cup competition with their all-important league fixtures, with the Scot hopeful his side can embark on "a good cup run", starting with a victory over the Baggies tomorrow.
Moyes, now in his second spell in charge of West Ham, said: "I think Slaven will get a good reception".
The Premier League side, who face Albion in the FA Cup this weekend, had an option to recall Diangana but have been pleased with the 21-year old's progress during Albion's promotion chasing season and believe he will benefit greater from remaining with Slaven Bilic until May.
The Hammers have been linked with a host of midfielders this month including Sander Berge, Joe Allen and Franck Kessie, but Soucek would be a very good signing for them if they can agree a deal for him. "I think everyone's well aware we have to play Liverpool on Wednesday and Brighton the Saturday after, so it begins to make you question if you can afford any more injuries, but ideally for the supporters we get through in the cup and do the best we can".
The Croatian said: "I can't deny that it will be a special game for me and for Julian [Dicks], but at the same time, it's also just a normal game".
"We've only got two or three midfield players", Moyes added.
Moyes will be without up to eight players through injury after Robert Snodgrass, Arthur Masukau and Angelo Ogbonna picked up knocks at Leicester in midweek.