Slaven Bilic has warned West Brom that West Ham are a different team to the one which capitulated against them in September.
The Hammers suffered a Hawthorns horror show and found themselves 4-0 down shortly after half-time before eventually losing 4-2.
But since then Bilic has been able to welcome back Andy Carroll from injury, with the striker scoring four times in his last four games including January's goal of the month against Crystal Palace.
West Ham have also bolstered their squad with January signings Jose Fonte and Robert Snodgrass, and put the Dimitri Payet saga firmly behind them.
Furthermore, they are now looking more at home at the London Stadium following their early-season problems and host West Brom on Saturday having climbed to ninth, just one place behind Tony Pulis' side.
"That September was very bad for us," said Hammers boss Bilic.
"We had pre-season injuries, players at the European Championship who didn't do a proper pre-season and got injured.
"A week before West Brom was the Watford game, when we were winning 2-0 and playing so good, and lost 4-2.
"That affects you like a chain reaction, there were a number of factors and it doesn't happen overnight to come back to the level required to have a good team. It took us a couple of months.
"We are a different team now, we have players fit, that is the key.
"Now we have to at least maintain it, try to avoid injuries, work hard and try to improve."
Bilic is hopeful Carroll will be fit to face the Baggies after suffering a groin problem which has prevented him from training this week.
The Croatian will also be keeping a close eye on another striker, Albion hitman Salomon Rondon who scored against West Ham in the reverse fixture and has seven for the season.
"A lot of people say they play one-way football, very simple, predictable," added Bilic.
"I don't find it that way. They are very versatile. They are at their best when they sit back and defend with numbers and go on counter-attacks, with Rondon or the wingers.
"Then you have set-pieces, and you have Rondon who can hurt you by himself, big time. They are a good team and the job Tony Pulis has done there is amazing."