The 29-year-old will start in the No.13 jersey against Newcastle in an elimination final at Eden Park on Sunday a transformed footballer, after being chopped and changed by the underperforming Gold Coast outfit for five seasons.
"When he was at the Titans I think Erin lost his identity in terms of who he is," Toopi told AAP.
"Am I a hooker? Am I a lock? Am I a bench player? Psychologically in those moments you are happy to play anywhere, but when given responsibility to own a starting position it's a huge confidence booster.
"Coach Andrew Webster has got the best out of all the players and Erin has shown that he wants to own that lock position."
In the past two seasons at the Warriors, across 50 games, Auckland-born Clark has averaged 135m compared to the 65m he managed at the Titans.
Incredibly he has notched 2686 post-contact metres in two Warriors seasons, well above the 2113m he made in 94 Titans games.
The New Zealand international started his career in the Warriors system and played NSW Cup in the halves. After playing one NRL game for the club he moved to the Titans where he played well but was never offered a regular starting spot.
After one match off the bench for the Warriors last season, he has played the last 49 in the No.13 jersey without missing a game.
"Erin would admit to that deeper connection coming back home for a second time," Toopi said.
"He has spread his wings and come back and flourished to become one of the game's elite and best in terms of what he offers."
While the Warriors players are part of a tightly run system, Clark naturally has attacking gifts that add to the powerful running and aggressive defence in the middle that has made him such a fearsome proposition.
"In his past he was a little nuggety six but didn't get a chance to play at any stage there with the Titans," Toopi said.
"When you play six for a long time it tells you that you have vision, skill and you are a runner.
"What Erin has been able to do at the Warriors is exploit those talents and show what skillset he can bring to the table. You see him go to the line and get short balls away.
"He has got an offload, he powers through, he has got a flick pass. He has got a grubber. He has been given the OK to do that."
Toopi, who suffered the heartbreak of losing the 2002 decider to the Sydney Roosters, explained what was required in a do-or-die final.
"I got caught up in the atmosphere of the 2002 grand final. You walk out on the field and there are 90,000 going crazy and all I could do was be in awe of the moment," Toopi said.
"Before you know it that 80 minutes is over and you have lost a grand final. It still is very raw 20-odd years later. These Warriors boys will want to walk off the field having no regrets at all."
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