The former Manchester City ace, who joined Borussia Dortmund during the summer after knocking back advances from English rivals, netted two goals and set up one more as the Young Lions beat Chile 4-0 on Sunday.
Sancho is expected to be recalled by Dortmund before the knockout stages get underway, however, having already been included on the German club's bench in the Bundesliga this term.
Cooper is not prepared to look that far ahead, though, telling reporters: "All of are here for the group stage at the moment. We need to qualify [for the knockout round] first. We are not thinking of anything else until we get out of the group stage.
"Nobody's going to get carried away with the win. Now we need to get the plan right for another really good test and recover well. It would be naive to look beyond the group stage now," Cooper said after their convincing result."