West Ham assistant manager Billy McKinlay concedes they face a major test at Bristol City tomorrow.
The Hammers face Bristol City in their Third Round FA Cup replay.
McKinlay said: "It's a difficult game. We had no surprises in the first game. I think they've fully deserved their draw.
"We had some opportunities to probably increase our lead after we scored early, but the game was really difficult and going there it will be a full house, a midweek FA Cup replay and a big game with a good atmosphere, so we're looking forward to it. We're confident we can produce a performance that will hopefully put us through."
The Scot added: "Lucas Paqueta is not available and the same for Jarrod Bowen. We'll determine their availability for future games after tomorrow.
"We're short a couple of players so we'll have to make some changes."