A much-needed win moved Ole Gunnar Solskjaer's men up to fifth.
Eden Hazard himself admitted after the game that solo effort against West Ham was "something special".
Victory ensured Chelsea moved into third in the Premier League, two points clear of Tottenham and three ahead of fifth-placed Arsenal in the race for a top-four finish.
Tomas Repka played three years at Fiorentina in Italy and five at West Ham United in London as well as turning out 46 times for his country.
A video clip containing audible expletives directed at Mohamed Salah includes comments against his Muslim religion.
The draw leaves league leaders Liverpool just three points clear of Manchester City.
West Ham were not the only top-flight side beaten by lower league opposition, with Everton losing 2-3 to Millwall.
Saturday's early kick-off saw teenage midfielder Declan Rice score his first West Ham goal in a 1-0 win at home to London rivals Arsenal.
Victory against Southampton saw the West Ham climb into ninth place in the Premier League table.
Leicester City's Premier League match away to Cardiff on Saturday will go ahead as planned.
Manchester City took the lead in the 17th minute with Aguero continuing his remarkable run of goalscoring form at the Etihad.
Ahead of Tuesday's UEFA Champions League clash with Valencia, Jose Mourinho insisted he doesn't fear for his job.
Manchester United suffered their third defeat of the Premier League season after losing 1-3 to West Ham United on Saturday.
Before this, West Ham had only won one of their previous 19 Premier League matches against Manchester United.
West Ham took advantage of Manchester United's poor play and thrashed them to clinch a 3-1 victory.
Chelsea enjoyed more than 70 per cent of possession in the first half but West Ham were dangerous when they were able to break out.
Olivier Giroud, who moved to Chelsea in January, believes the battle with Alvaro Morata is positive for the team.
Andriy Yarmolenko scored twice for West Ham as they climbed off the foot of the English Premier League table with a 3-1 win away to Everton.