The Hammers, who finished seventh last season and moved to the Olympic Stadium over the summer, were defeated for the fourth time in a row in the Premier League and are in the relegation zone.
[RELATED: West Ham fall to dismal new defeat as Southampton pile on home pain]
Bilic told Sky Sports: "We deserved to be defeated. One by one they (the players) gave everything but it's not enough.
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"It's hard to change it. The team is down. We have good weeks of training but when the game comes it's simply not good enough.
“We have to work hard but it's not happening."
The Croatian manager said that it could take time to turn things around as his team is in a bit of a rut. "We are in a really bad spell," he added. "We are a team that is expecting something to happen by default. We don't have the confidence and it's a chain reaction.
"It's not a magic wand thing. All you can do is stick together and work hard."
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