Wests Tigers co-captain Moses Mbye will come back into contention for another positional switch as the NRL's blocking of the Paul Momirovski-Harry Grant player swap shakes up Michael Maguire's starting side.

Despite being confident of the landmark "loan" style arrangement going through three weeks ago, the Storm were informed on Monday night that the proposal in its current format would not be approved by NRL salary cap auditor Richard Gardham.

It's understood an estimated $15,000 component of Momirovski's salary has been flagged by Rugby League Central, with Melbourne and the NRL unable to agree on an interpretation that fits into their salary cap.

With round one less than a month away, plans for Momirovski and Grant to trade clubs in 2020 before returning to the Tigers and Storm respectively are set to be reluctantly abandoned.

As a result, Momirovski – who is on the verge of agreeing to a two-year extension as reported by NRL.com over the weekend – will push for his regular left centre spot in Maguire's line-up as star signing Joey Leilua makes himself at home on the right.

While Mbye finished 2019 on the left edge a switch to hooker looms once more after splitting his pre-season training between the two positions.

A shortage of hooking options at Concord was what made Grant – Cameron Smith's long-term successor at the Storm – so appealing for Maguire given the Tigers have plenty of backline candidates.

Mbye began training at dummy-half late last year when Josh Reynolds' playing future was clouded by domestic assault allegations which he will contest in court in April.

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The NRL recently cleared Reynolds to play while his legal matter is before the courts, bringing the veteran utility into contention for the No.9 jumper as well.

However, Reynolds has played just 12 games since moving to the Tigers two years ago amid a raft of injuries, prompting the club to approach him about a potential early release last July.

A bench utility role may well better suit the former NSW Origin five-eighth than the defensive rigours of playing hooker given he played through a shoulder injury for a month in 2018 that eventually needed season-ending surgery.

Reynolds is slated to start at five-eighth in this Saturday's trial against Penrith and share dummy-half duties with late bloomer Billy Walters, who to date has played the majority of his football in the halves.

Local junior Adam Doueihi is also due for his first run in club colours on Saturday since returning from South Sydney.

Doueihi's arrival at Concord makes a move to fullback unlikely once more for Mbye, who has played five different positions in seven years of first grade.

Mbye started at No.9 as a rookie replacement for Michael Ennis in Canterbury's 2014 grand final loss to the Rabbitohs, and last played in the forwards in 2017.

He also impressed when pitched into the centres for Queensland during Origin III last year.