Just a few weeks ago, he was contemplating struggling to even get a game this year for Huddersfield Giants where the Australian was out of favour with head coach Simon Woolford.
Yet now, while his winless former club remain rooted to the foot of the table, Rankin finds himself an integral part of a team flying high at the top.
Leaders Castleford will seek to maintain their 100 per cent winning start when they head to Warrington Wolves tonight with the 27-year-old growing in confidence as their new scrum-half.
Given England No 7 Luke Gale and Jamie Ellis both suffered serious injuries during pre-season, Tigers moved for Rankin in January in an exchange deal that saw Joe Wardle go the other way.
As Tigers aim for a fifth straight win, Rankin admitted: “There’s no complaints from me; it has been a really good start.
“It’s been a big six weeks for me since I signed for Cas, just trying to get to know the plays, the coaching staff and the players.
“I think slowly it’s becoming better every week. Obviously, I am still building, but it has been a lot easier with the start we’ve had.
“I am slowly implementing different things the coaching staff have given me and bringing them out in my game. Hopefully, over the next couple of weeks, we can see more of it and more wins.”
For someone who has been so versatile throughout his career – Rankin has played half-back, full-back, centre and even wing during his time in the UK with Hull FC and Huddersfield – the former Gold Coast Titans player is relishing being given one firm role at Wheldon Road.
Gale is out for the season and Ellis could be sidelined until July following knee surgery so Castleford coach Daryl Powell has pinned faith in Rankin as the half-back partner for Super League ‘Young Player of the Year’ Jake Trueman.
They have been paired together for the opening four games and, with Powell plus assistants Ryan Sheridan and Danny Orr all being former Great Britain half-backs, he appreciates not just the certainty shown in him but their valuable input.
Rankin said: “That has been really good. I’ve been mixed in the halves and full-back pretty much the whole of my career and never really settled on one position.
“I have come here and Ryan Sheridan has been really good helping me implement some things in my game as a half. He and Powelly and the coaching staff in general have taken my game to a new level that I’m hoping to bring out the next couple of weeks and rest of the season.
“They haven’t flooded my head with information overload; it has been a drip-feeding process for me and they have pretty much backed me to go out there with my ability and help win games.
“At the moment, it is going well. When the grounds get a bit firmer and the weather gets a bit sunnier I think that’s when they’ll see the best of me. But, at the moment, I’m happy with the way everything’s going, leading the team around and helping them get wins.”
Warrington have dropped to third after suffering their first loss at Catalans Dragons on Saturday but they will be Castleford’s biggest test yet.
“They have shown over the last few years what a quality side they are,” said Rankin, who returned to the UK at Huddersfield from Wests Tigers in 2017.
“They’ve picked up where they left off from last year and got some good recruits in Blake Austin and Lama Tasi.
“They had a bit of a blip against Catalans, but that’s always a tough place to go.
“We’ve had a pretty short turnaround, like they have, but we know we’ve got a good enough side to go there and win the game and keep our winning record intact.”
Rankin scored his second try in Castleford colours during Friday’s 32-16 win over Hull KR, an effort that all the more special given his time with their fierce rivals Hull in 2014 and 2015.
“It was fantastic to score against them and it was probably my favourite win of the year so far!” he said.
“There was a bit (of niggle) in that game but it was just important to get the two points to continue this great start of the season for the boys.”