The response was emphatic. The Hammers won four out of their next five games - beating Bundesliga side Freiburg 2-0 in the Europa League, dismantling Wolves 3-0 and recording impressive 2-0 wins at home to Manchester United and away at Arsenal.
The outlier was another five goals shipped at Anfield, as they lost 5-1 in the Carabao Cup quarter-finals.
In those five matches, Jarrod Bowen contributed directly to five goals - scoring three himself and assisting two more - while playing a key role in getting Moyes' side back on track.
Now, after the 6-0 debacle in the reverse fixture at home to Arsenal on Sunday, West Ham desperately need a response from the team, and in particularly their main man, once more.
Since that win at Emirates Stadium, Bowen has not scored or assisted in any of the five games he has played in - culminating in Sunday's effective no-show. West Ham have not won any of these games.
The correlation between his output and the team's struggles is clear, and only exacerbated without the creative influence of the injured Lucas Paqueta or the threat of Mohammed Kudus who has struggled to get up speed since his return from the Africa Cup of Nations three matches ago.
The sight of fans streaming out of the London Stadium before half-time in what became the Hammers' heaviest home Premier League defeat and joint-heaviest of all time will worry Moyes, who remains under fire from big sections of the fanbase.
The boss has to see the next four Premier League games, all against sides currently in the bottom seven, as an opportunity to kickstart a season threatening to fade away.
Three of these come before the Hammers continue their Europa League campaign at the last-16 stage. The response to this latest humiliation could define West Ham's season.