Kalyn Ponga is set to make the long-awaited shift from fullback to five-eighth, however Newcastle icon Andrew Johns has warned it won't be all smooth sailing.

The Newcastle captain is set to finally make the move into the halves after a trial run at the start of 2019, partnering Jackson Hastings at the scrum base, however Ponga's immense natural talent doesn't mean the transition will be an easy one.

The fullback-turned-five-eighth earned comparisons to Darren Lockyer early in his career, which pushed then-coach Nathan Brown into shifting the young gun into the front-line.

NRL Rd 4 - Raiders v Knights
SYDNEY, AUSTRALIA - JUNE 07: Kalyn Ponga of the Knights scores a try during the round four NRL match between the Canberra Raiders and the Newcastle Knights at Campbelltown Stadium on June 07, 2020 in Sydney, Australia. (Photo by Mark Kolbe/Getty Images)

Unfortunately Ponga, who was just 20 at the time, was still too raw to make the move a permanent one, with an Edrick Lee intercept try in the opening round the only thing stopping Ponga from going 0-3 in the halves before being shifted back.

His combination with Hastings has already been described as the 'NRL's odd couple', Ponga's laid back approach a contrast to Hastings hunger and intensity, and Adam O'Brien is liking what he sees.

โ€œThey're yin and yang: one is the complete footy head who is very comfortable in directing the team, and the other is a freelancer who wants to freelance, so they marry up well,โ€ O'Brien told The Sun-Herald.

โ€œIn the past we would have had six weeks to get this right, but we've had five months. And if you're going to make the change, you might as well take five months.

โ€œHe's put size on in the gym, he's done a heap of contact and a heap of general-play kicking. He'll float and we won't lock him into one side of the field.โ€

Andrew Johns is a big fan of the pairing, however he's concerned about Ponga's biggest problem in the front-line - defence.

โ€œWhat Kalyn did at club level and in Origin last year โ€“ his game in attack will not change much with him moving from fullback to five-eighth,โ€ Johns told The Sun-Herald.

SYDNEY, AUSTRALIA - MARCH 21: Commentator Andrew Johns looks on before the round two NRL match between the St George Illawarra Dragons and the South Sydney Rabbitohs at Netstrata Jubilee Stadium on March 21, 2019 in Sydney, Australia. (Photo by Cameron Spencer/Getty Images)

โ€œHe does things now at training where you just shake your head because he's so good. He's an exceptional talent.

โ€œBut the big test for Kalyn will be defence. He's got timing, he's got the footwork, and that's the recipe you need to be a good defender. He'll get it done.โ€

The halves pairing is set to debut against the Parramatta Eels on Friday night as O'Brien finalises his side for their opening round clash with the New Zealand Warriors, with question marks lingering over the left edge, specially the wing and back-row.