Sam Allardyce admits tired West Ham "copped it" at West Brom and believes top flight clubs have fallen in the FA Cup because of their packed schedule.
The Hammers were dumped out by the Baggies following a 4-0 defeat at The Hawthorns on Saturday.
Allardyce was jeered by his own fans and his substitutions booed during the game despite the Hammers' fine form in the Premier League.
Chelsea, Manchester City, Southampton, Tottenham and QPR are among several top-flight clubs who had already fallen by the wayside before the fifth round.
And after missing out on a quarterfinal spot following their third game in six days, Allardyce believes West Ham suffered burnout.
"We have been riding that wave from the third round," he said. "Has anyone identified why there was so many shocks in the third round? Because we had to play on Thursday and the Football League teams didn't because they were all off.
"You had that many shocks on the Saturday because all the Premier League clubs were playing on New Year's Day. That gave us another boost, that the bigger clubs were out, but we copped it this time, not New Year."
Allardyce again dismissed the criticism from the travelling supporters and insisted it comes with the territory.
"When fans are not happy they show their disappointment, it's the same all the way across the country," said Allardyce, who added Morgan Amalfitano will be disciplined after his second-half red card.
"My job as the manager is to deal and cope with the players to get them on the pitch to entertain and to keep them winning as much as we can, which is what we've done for 85-90 percent of the season.
"We have had a disappointment and we could overcome it if it was a Premier League game but we can't because it's a cup game. That's why the disappointment is even greater for us. We have to live and cope with it."
Brown Ideye scored twice to make it four goals in three games since he was on the verge of leaving West Brom on deadline day.
James Morrison and Saido Berahino added to the rout and head coach Tony Pulis admits they need the luck of the draw if they want to keep going in the competition.
"It's about the draw. Having been in it one year we did brilliantly at Stoke and we pulled Chelsea away in the quarterfinal and lost," said Pulis, who took Stoke to the FA Cup final in 2011, where they lost to Manchester City.
"We need a slice of luck and if we have a good home game we have a chance. We need a break and a good draw.
"We haven't got a strong and as big a squad as Sam has, so we have got to be lucky. We have to be lucky with players."