It began to have an effect as Letoa won the fourth round, making Berridge back up for the first time, having landed a solid left early on.
But 'the Butcher' always has that cement in his hands and early in the fifth round, after both fighters were again warned for head clashes, Berridge tried a lead uppercut with the right on the ducking Letoa, catching him flush and dropping the Samoan.
Letoa staggered up but after few more hard shots in the corner the referee waved it off, 1m 10s into the round.
"Trying to find that range, I got a shot off that I've been practising, and it paid off," Berridge said in his interview afterwards.
Watching back in Wanganui, his cousin and Rise of the Fallen co-promotor Paul Berridge said Letoa was no easy fight for the comeback.
"This guy he fought replaced him on the Adrian Taihia card [in May last year].
"Adrian went the distance with him.
"Rob, pretty much the gameplan was to box and get the ring rust out."
Robert Berridge will now return home to prepare for his April 25 bout in Wanganui against New Zealand No 4 light-heavyweight Andrew Robinson, in a fight which could have national championship implications.
Paul Berridge has also announced the names taking part in the eight corporate fights on the card.
Rise of the Fallen will be held at Springvale Stadium.