The West London club looked set to claim three points on Monday before James Collins equalised for the Hammers in the 77th minute of the game after Eden Hazard's earlier penalty, however, Diego Costa won the game for his side by scoring a winner in the 89th minute of the game.
"It was a blow because it was late in the game," he told the club's official website of the Collins leveller.
"It was disappointing because up until that point we had been snuffing out any danger and we were solid.
"Unfortunately we conceded but we showed great character to come back and win the game, we got what we deserved. We can take a lot of confidence from the game."