England youth international striker Brewster, who turned 19 on Monday, made his eagerly-awaited comeback after 14 months out injured in a friendly for the under-23s last week.
Brewster, who scored twice, took a blow to the hip but it's only a minor setback and Klopp is relishing the impact he will make over the coming months and years.
“It was good to see Rhian back," Klopp said.
“It's nice having him in training. It was his birthday this week, 19 years old, crazy. So much to come. Get him fit, keep him fit and then the door is wide open for him."