Just a fortnight after the Hammers went into the international break off the back of a formidable 4-1 victory over Ipswich Town, Julen Lopetegui saw Spurs beat his fragile team by an identical, sorry scoreline.
“It’s been very frustrating and, as a coach, I have to be concerned,” conceded the shell-shocked Spaniard following the claret and blue capitulation.
“Defensively, we have to do better and focus on our concentration. We need to be calmer, show more personality and display more character.
“If I’m honest, we must have better moments than today. The Premier League season is very long but, only at the end of it, will it be time for us to be judged on where we finally finish.”
Certainly, there was little sign of the things to come, when Mohammed Kudus slotted the visitors in front on 18 minutes.
But it all went downhill for both the Hammers head coach and his subsequently red-carded Ghanaian goal-getter, after that.
Dejan Kulusevski levelled just before the break and, after Yves Bissouma put Spurs ahead early in the second half, an Alphonse Areola own goal plus a strike from the fit-again Heung-Min Son then quickly put the contest out of reach.
“We played one of the Premier League’s best attacking-phase teams but we needed to stay mentally strong after we conceded that second goal because we still had lots of time left to get back into the game,” added Lopetegui.
“When we’re suffering, we must handle these bad moments in a much better way and, for sure, it’s not good to end up conceding three goals in eight minutes.
“The first half was interesting, the players did very well and we can still take away some good things from today but that’s not enough because everybody needs to play well for the full 90 minutes and more in every game.
"We must stay competitive and keep our mentality right until the end. Now we will go away and work very hard for our next challenge."
A fourth reverse of the season leaves the Hammers in 15th-place with eight points from as many games, but they must now face Manchester United at London Stadium on Sunday (2pm) without the suspended Kudus, following his skirmishes with Micky van de Ven and substitute Pape Matar Sarr in a feisty finale.
“It is not good for him or the club and we will speak together,” concluded Lopetegui, who waits to learn whether the enraged 38-cap Ghana international will be banned for more than three matches as a result of his derby dismissal for violent conduct.