The left-back returned from a hamstring injury to face Leeds on New Year's Day but lasted just 18 minutes before being replaced by Conor Townsend.
Slaven Bilic revealed the Baggies are awaiting the outcome of his scan, but the former Arsenal man will definitely not feature at The Valley in the weekend's third-round tie.
Attacker Diangana has not yet been able to train due to the back problem that forced him off against Birmingham last month.
He will not be involved against fellow Championship outfit Charlton, but will be fit to return for the following game – also at the home of the Addicks, in the league six days later.
There has been no further movement on West Ham's decision to recall Diangana from his stint at The Hawthorns. The Premier League side have two weeks in the January window to trigger the recall.
Bilic said: "We are waiting for Kieran's scan and then we'll know.
"Apart from that everything is alright apart from fatigue. Nobody reported to me with important injuries. It's only Kieran.
"The rest, of course the boys are tired, we played (all) the games. It's not only physically but also mentally but no injuries which is very important."
On Diangana featuring, the boss added: "No, but definitely for the next game.
"His progress is going as expected. At the beginning you only know four weeks, and it's not a big injury, but it's not he's had a setback, it's all good, but you don't want to rush too much.
"He missed those couple of sessions, proper sessions, that we didn't have anyway in this period on the pitch all together, apart from days before game."
Bilic continued: “We have to strike a balance between changes and respecting the competition. Everybody is looking forward to it, everybody wants to be part of it and everybody wants to have a good run.
“Basically we will try to field a competitive team with chances to progress and at the same time rest some players.”