The Baggies boss handed four players their first ever taste of senior football in an XI which included a smattering of experienced performers.
Arsenal fielded their strongest team at The Hawthorns and ran out comfortable winners thanks to a hat-trick from Pierre-Emerick Aubameyang.
Speaking afterward, Ismael made clear Albion’s priority this season is promotion from the Championship.
He said: “The final thing is to thank the fans. They understood our priority this season is clearly the Championship.
“At the end they applauded the young lads for their performance. The guys tried to give everything. Now we move on and the focus is on Saturday and Peterborough.”
Albion’s team featured six debutants along, with six of the starting XI aged either or under.
The Baggies gave as good as they got early on but fell behind when Aubameyang netted from close range.
A quickfire double on the stroke of half-time from Aubameyang and Nicolas Pepe put the Gunners in command, with the former completing his treble in between second half goals from Bukayo Saka and Alexandre Lacazette.
Asked if he was content with the performance, if not the result, Ismael replied: “We need to distinguish between the two situations. The first one is the performance.
“In the first half especially at some points it looked very good. Very good pressing and intensity.
“We won the ball and created the first big chance in the game. We conceded the first goal with a massive, massive mistake and we need to accept this with the young lads.
“Through the 90 minutes we struggled at points but it is all about mentality, to stay strong and stay in the game.
“We came back in the second half with some good chances to score and give a good feeling to the lads.
“For us it is important to reach our purpose. Snods played 70 minutes, (Adam) Reach played 90, so did Cedric (Kipre). It is important to put the player on a good fitness level.”