The US international striker, recently signed on loan from MLS side Orlando City, was brought in for the final half hour in the 1-0 FA Cup loss to the Blues at Oakwell.
Ismael admits that the 20-year-old had some initial problems adapting, but saw some positive signs towards the end of the game to give him something to build on.
Ismael, whose side return to Championship action with a tough trip to Brentford on Sunday, said: "It was important for him, first of all, to adapt to the way we need to play.
"At the beginning, he had some problems and then it was not so bad and at the end, it was much, much better.
"We could see what we believe in him, with his power, speed and physicality to give us more options in our front three.
On a night which he believes that aid all of his young players going forward in terms of their mentality and progression, the Frenchman added: "You learn a lot at this level and it is a good thing as the players recognise exactly what they need to make the next step and it will serve as a big purpose for them to play in the Premier League in two, three or four years. It will help put them in the right direction.
"They have played Chelsea twice this year with two different results and ways to play football and it is all about staying true to yourself and playing with courage and playing with your principles.
"After the game, it was clear to see how the guys are improving in terms of their performances and their development is clearly visible. It is a long process and in the last steps in this performance are that you have to be clinical and score when you get the chance.
"We created big chances against Chelsea and that is why we have more belief now. We can compete at this level, be unpleasant against Chelsea and take it into the league."