Clearly, the loss of influential ‘marquee’ signing Merrin is a significant one for Rhinos head coach Richard Agar but not one that was entirely unexpected.
The ex-Australia loose forward had explored moving back to the NRL during the off-season on “compassionate grounds.
Just five weeks ago, when nothing materialised, the club had confirmed he would play on with them in 2020.
Indeed, Merrin - only one season into a lucrative four-year deal after joining from Penrith Panthers - returned to the UK and started pre-season training but late interest from his former club St George-Illawarra has seen a deal resurrected.
Understandably, Rhinos would not sanction the move until they, in turn, secured New South Wales State of Origin forward Prior but, with that now in place, the switch is complete.
Prior, 32, has played more than 250 NRL games and won a Grand Final with St George-Illawarra under Wayne Bennett in 2010 before adding another title with Cronulla three years ago.
He represented New South Wales last year and Rhinos director of rugby Kevin Sinfield said: “We’re delighted to secure a player of Matt’s undeniable experience on a two-year contract. He is someone we have looked at for a while and will be an uncompromising addition to our squad.
“Having spoken to him over recent weeks, I know how much he’s looking forward to joining and the new challenge of playing in the Betfred Super League.
“It is disappointing to lose Trent but we fully understand his reasons for returning home. He leaves with our best wishes for him, Jess and their new family.”
Prior was an ever-present for the Sharks last season, where he has played since 2014, starting all but one game.
He teams up again with his former Cronulla team-mate Ava Seumanufagai after the front-row moved to Headingley last summer and joins the club subject to completing a medical.
“I know that Leeds Rhinos have a fantastic history but have had some tough times in recent years,” said Prior, who - the club point out - is not a direct replacement for Merrin.
“Hopefully I can play my part in lifting the club’s fortunes and get us back to challenging for silverware again. I know Ava Seumanufagai and Adam Cuthbertson well so it will be good to catch up with those guys. I nearly signed for the Rhinos a couple of years ago but we didn’t get the deal done so this is something I have always had in my mind.
“It is an exciting time to be moving to Super League with players like Sonny Bill Williams, Gareth Widdop and George Burgess coming into an unforgiving competition and I can’t wait to get involved.”
Prior and Merrin, 30, were St George-Illawarra team-mates for five years, including that title-winning campaign, and both hail from Wollongong.
Merrin wants to return home to be closer to family with his partner expecting a baby.
Agar added: “On behalf of everyone at Rhinos, we’d like to wish Trent and his partner Jess all the best for their future back in Australia. I know this is something Trent has tried hard to resolve but in the end his family comes first and he’ll leave with our best wishes.
“We were already in the process of signing Matt and I was looking forward to seeing him lining up alongside Trent but unfortunately that will not be possible now. However, Kevin Sinfield is working hard behind the scenes to complete our squad. Unlike most of our rivals, we still have flexibility to bring in players, which we did successfully with Rhyse Martin and Ava Seumanufagai last season.
“And the market is still very much open in terms of players availability both here and in the NRL if the right player becomes available.”