Barnsley first-team coach Jamie Clapham described substitute Adam Hammill as "exceptional" following his match-winning cameo in their 3-2 Carabao Cup victory over Derby.
Hammill was thrown into the action in the 61st minute with Barnsley trailing 2-1 but, after Tom Bradshaw had drawn the hosts level, the 29-year-old scored a late winner to seal a third-round tie against Tottenham.
Clapham said: "Adam has come on today and scored the winner and his performances lately have been exceptional so he has to keep that going.
"But we know that everyone will be needed. It's a difficult league and a difficult campaign."
Derby opened the scoring in the ninth minute with Chris Martin finding Johnny Russell inside the area and he curled the ball into the net.
It did not take long for Barnsley to equalise, though, with Adam Jackson heading home a Ryan Hedges corner in the 18th minute.
The away side hit back late in the half to take the lead again with Mason Bennett getting on the end of a wonderful Ikechi Anya delivery.
It took until the 68th minute for a reply from Barnsley, with Bradshaw sliding in a far post cross from Harvey Barnes to make it 2-2.
Hammill then snatched victory for the hosts when he curled in a brilliant effort from outside the area, to the delight of the home support.
Clapham added: "The amount of players they (Derby) have at their disposal, we knew it was going to be difficult.
"They changed 11 players and still had internationals and hundreds of Premiership and Championship games under their belt.
"It was a good test and all the lads in the dressing room really stood up to it.
"We controlled the game and took the opportunities when we could."
On the the third round game at Wembley, Clapham said: "With it being a late tie we knew what the reward would be, but we've got to recover well and focus on Saturday."