Huddersfield boss David Wagner was left to lament a number of costly errors which were punished by a ruthless West Ham side who ran out 1-4 victors at the John Smith's Stadium on Saturday.
The Terriers gifted the Hammers their opening goal after a defensive mix-up from a goal kick between Jonas Lossl and Joe Lolley which led to Mark Noble finding the back of the net.
Despite levelling prior to the break through Lolley, a collapse at the back paved the way for a heavy defeat as Marko Arnautovic doubled the Hammers' lead just 11 seconds into the term, before Manuel Lanzini scored twice.
Wagner was ultimately left to rue the mistakes which handed the victory to West Ham as he told Sky Sports: "It was a frustrating day because we made too many easy mistakes. The first is an individual mistake that should never happen.
"With the second, 11 seconds into the second half, it was a very simple knock-down and we needed to be stronger and see the danger earlier.
"We tried to play offside for the third. West Ham have creative individuals who today were able to hurt us. We had too many players who were below par today."
Worst performance of the season I feel like crying— Macca🇬🇧 (@HtafcMacca) January 13, 2018
The Terriers are now without a league win in their last five, where they have conceded nine goals in that time - a leaky defence which Wagner knows he must rectify if they are to see an upturn in results.
He added: "We have to make sure this never happens again, but we know exactly what went wrong today.
"Unfortunately not everything in football goes to plan. The second goal we've been speaking about in training all week.
"Transition was a big part of training this week, but you see the goals we've conceded today and you can't make these mistakes if you want to pick up points in the Premier League."
Huddersfield sit in 14th position in the league table but remain just four points above the relegation zone.