Percival, 18, was a major positive for Saints despite getting beat 20-12 having made numerous clean breaks and putting wing partner Francis Meli over for a brace of tries.
Brown said: “We put him in there for a reason – because we thought he’d do well. Did we expect him to go out there and be that good? Well you never expect that out of any 18-year-old.
“We could have left Josh Jones and Jordan Turner in the centres if we’d wanted to and somebody probably thought it was a silly thing at the time. In hindsight they’d probably say it’s a great decision.
“We were confident he’d bring something different to the team and he had a good game. But as is always the case with young kids, it gets a lot harder before it gets easier.”