Senegal international Kouyate is normally utilised as a central midfielder, but injuries to James Collins and Winston Reid meant he was needed to cover in defence.
The former Anderlecht man showed his physical presence at the other end of the pitch to open the scoring with a superb turn and volley in the 1-1 draw at Upton Park.
However, it was the solid display for West Ham's rearguard that caught the attention of manager Allardyce.
"I think he filled in there early on in the season for 10 or 15 minutes, but we know that he played for Anderlecht and he played for Senegal there," Allardyce said.
"What we didn't know was can he play with the right sort of tactical awareness and discipline you have to play with in the Premier League as a central defender and he proved that he could.
"The icing on the cake for him was the quality of his goal. In such a tight area, to flick it round and volley it in, in such a short space, was a terrific piece of skill. At that time it was nothing more than we deserved."
Kouyate has made 17 Premier League appearances since arriving at West Ham from Anderlecht in June.
