Salah, who has not been at his best since returning from injury last month, was brought on in the 79th minute, just after the Hammers' second goal levelled the game
The Argentine international now faces a three-match ban that would see him miss Premier League games against Manchester United and Bournemouth and a League Cup third-round tie against Swansea City.
On Monday, Aguero withdrew from the World Cup qualifiers against Uruguay and Venezuela due to a calf injury.
Argentina host Uruguay on Thursday and then visit Venezuela five days later.