Cesar Azpilicueta had prodded the hosts ahead following Alvaro Morata’s knock down, and the Spaniard dedicated his goal to the club’s former England midfielder Ray Wilkins, who died on Wednesday aged 61.
There was also a minute’s applause prior to kick-off, with the Chelsea players wearing black armbands in memory of Wilkins.
However, Hernandez, on as a substitute, struck his ninth career goal against the Blues to earn a point for the Hammers.
The Mexican’s effort, driven into the corner after Marko Arnautovic’s fine cut-back, moves David Moyes’ team six points clear of the relegation places.
It was only West Ham’s third touch inside the Chelsea’s penalty area.
In contrast, Antonio Conte’s men – who are in fifth but 10 points behind Tottenham and Liverpool above them – had 23 shots on goal and were good value for their lead for long periods.
And but for a combination of profligate finishing and excellent goalkeeping from West Ham keeper Joe Hart – on loan from league leaders Manchester City – the Blues would have realised that aim.
Moyes’ horrendous record at Stamford Bridge looked well on course to stretch to a ninth defeat in a 15-game winless run.
The Scot has still not managed a victory from 30 outings against a ‘big six’ side since a 2-1 win for Everton over Manchester City in December 2010 – but Hernandez’s strike altered the complexion of the game while delivering a precious point.
The 29-year-old, whose future and relationship with his manager has been questioned, once again showed his predatory instincts to turn the ball beyond Thibaut Courtois three minutes after coming on.
Hernandez has now appeared four times as a substitute at Stamford Bridge in the league – and scored on all four occasions.
This was the former Manchester United forward’s ninth in 14 appearances against Chelsea, more than he has managed against any other Premier League opponent.
