The Titans stunned ladder leaders Penrith 19-18, with 20-year-old Harrison snaring the win with 19 seconds left on the clock.
Campbell said he wasn't surprised his rookie halves partner, playing just his sixth NRL match, was able to pull off such a high pressure move.
The 26-year-old felt Harrison, and the entire team, would take confidence in being able to ice the win against the title favourites, just one round after letting a late lead slip against Wests Tigers.
"I think it'll fast-track his development," Campbell said of Harrison.
"Last week we were in a game similar to that, a very tight contest, and as a team we made mistakes, so having a game like that again and being able to ice the opportunities and play the way we did, we learnt from the week before.
"I think that's just going to fast-track not just him but us as a footy team."
Starting his NRL career with the Titans in 2021 as a fullback, Campbell opened this season at halfback but said he felt his own game flourished since the arrival of the youngster in round 10.
"It's been unreal to work alongside him (Harrison) - I'm not really surprised by how he played, just the way he comes in, trains, how he prepares for a game," Campbell said.
"It's been a lot easier for me to just play what I'm good at, running the ball and not doing too much organising but he's been massive not just for myself but for the whole team.
"Personally I think I'm a five-eighth so I'd like to stay there."
With the Titans sitting 15th and eight points outside the top eight, Campbell said it was still important to continue to build their game under new coach Josh Hannay.
"This year we're starting to really have an identity about how we want to play and who we want to be as a football team," he said.
"Even a lot of games this year, we've been right in the contest, so I'm really, really proud of the way we're going.
"I know it's a bit late in the season, but hopefully we can go on a roll and we can keep winning games."
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