West Brom defender Branislav Ivanovic and midfielder Matheus Pereira have both tested positive for Covid-19.
Manager Slaven Bilic said the club received the results last week and the pair are under going a period of 10 days in self-isolation.
"It's a setback," said the Croat boss, before Sunday's game against Tottenham.
"We found out on Tuesday and Wednesday. We have put a team out that is very good. There's every chance we can get something out of the game."
- Watch 13 first-round ties on BBC iPlayer and the BBC Sport website and app this weekend.