Ampadu lit up the Cup tie with a crunching challenge on Cherries striker Jermain Defoe.
Cahill remarked to the London Evening Standard: “Yes, he's the same in training — Ethan loves a 50-50. He goes tight. You just see good aggression, he's competitive. He wants to win matches, he wants to win the ball.
“Apart from the one on Jermain, he timed some tremendous tackles, especially in the second half, when we were defending the box. He grew stronger as the game went on.
“Did that tackle on Jermain show his lack of fear? Yes. But he is 17 and looking to learn all the time. I'm sure there were times in that game he would have wanted to go tighter on somebody but he would have had the yellow in the back of his mind. I'm sure in the next game he will go steady early on."
Cahill has a word of caution for those expecting too much too soon from the Welsh teenager.
He said: “When you're at a big club, you're shot right up at the top of a pedestal but can then be shot down. Everyone should keep steady.
“Ethan is learning. He had a great performance against Bournemouth and should be proud. There were many things that happened in the match that he will take away and use in the future. I understand people will ask more about him but it's just one game."