Bertschin recalls McClean's superb performance in their 6-3 win over eventual Premier League reserve-team champions Manchester United.
"The Manchester United game was excellent," he told safc.com. "We won with a decent mix of youth and experience.
"James McClean coming in was another highlight for me - he was a young, hungry, determined player who wanted to make an impact.
"There's no doubt he did that. In that Manchester United game, he was frightening.
"His attitude was refreshing because he was so hungry to do well and I'm so pleased he's done that.