When Ireland take on Moldova this Friday, there are likely to be some new faces involved up front for Martin O’Neill’s side.

Assistant manager Roy Keane has revealed that he expects some first-time caps to be handed out in the World Cup qualifier, with Scott Hogan, Aidan O'Brien and Seanie Maguire all vying for a place up front.

The uncertainty over Shane Long’s fitness, coupled with the absence of Jon Walters and the retirement of Kevin Doyle leaves Ireland looking very short on options in attack.

All of which makes it even more puzzling when trying to assess why the most consistent Irish goalscorer over the last three seasons still can’t earn a place in Martin O’Neill’s squad.

Adam Rooney couldn’t have timed his weekend hat-trick for Aberdeen better if he’d been seeking to underline to the questions surrounding his constant omission from the Ireland squad.

The 29-year-old Dubliner scored all three goals in his side’s 3-0 victory over St Johnstone, a result which took Aberdeen level on points with Celtic at the top of the SPL.

It was a welcome return to action for Rooney whose start to the season was delayed by a thigh muscle which ruled him out for five weeks but it didn’t take long for the striker to hit the goal trail soon after his recovery.

That Rooney would make such an impressive return would come as no surprise to observers who have followed him over the last three or four years in Scotland.

This is a player after all, who is close to averaging a goal every two games since 2014.

Rooney’s goalscoring record in the Scottish topflight would put many a striker to shame, scoring 28 goals in the 2014/15 season, 20 goals in 2015/16 and 20 goals last season.

His weekend hat-trick has him up to four goals from six appearances this term, despite missing a good chunk of pre-season and at this early stage he’s again on course for another 20 goal season.

By all measures, Rooney is Ireland’s most prolific goal-scorer at club level so his absence from the full Ireland squad remains baffling.

Rooney’s first international call-up came when O’Neill included him in his extended squad for a Euro 2016 qualifier against Scotland in 2015 and, as has become a familiar situation for the striker, he was cut from the final squad.

That’s as close as the frontman has come to making an international debut for his country and since then it’s been a familiar pattern for Rooney as he’s often named in a training squads and then not been considered for games.

"If Adam Rooney gets a chance it is up to him to take it" - Martin O'Neill

Rooney was again named in an extended squad for last year’s World Cup qualification double header with Georgia and Moldova and at the time O’Neill challenged the strike to take his chance to make a mark.

"If Adam Rooney gets a chance it is up to him to take it," the Irish boss said. "I don’t think I would be giving away too many secrets when I say that maybe there’s a dearth of Irish international players capable of playing in that position.

"Adam comes in and, if he gets an opportunity, I’m sure he’d like to shine."

That opportunity has yet to come for Rooney and under the current management team it’s debatable as to whether or not it ever will.

There have been several theories thrown about as to why O’Neill is so reluctant to give such a prolific goal-scorer a chance, chief of which is the league in which he’s plying his trade.

Sean Maguire’s sudden elevation to the Irish squad after a move from Cork City to Preston certainly added further fuel to the belief that it’s England or bust for the Irish manager, while Rooney’s former Aberdeen team-mate Jonny Hayes has similarly struggled to gain O’Neill’s attention.

The SPL is obviously a step below the English Premier League and yet it’s where O’Neill enjoyed his most successful spell as manager, leading Celtic to three league titles in five years in an era when Rangers offered stiff competition.

The Scottish league of today is not as competitive with Celtic dominating and Rooney’s Aberdeen currently taking up the mantle of the best of the rest, and Celtic aside, the standard would probably be in line with mid-table Championship teams.

However that hasn’t doesn’t mean there aren’t some diamonds in the rough and Scotland manager Gordan Strachan has been happy to give players like Christophe Berra, Steven Whittaker and John McGinn a chance.

Those players have helped Scotland mount a strong comeback in their World Cup qualifying group and they go into the final two games knowing that two wins will almost certainly see them earn a play-off place.

Rooney’s rivals for a place in the Ireland squad aren’t playing for teams that are streets above Aberdeen and their goal records can’t compare.

Aiden O’Brien has spent the last two seasons in League One with Millwall and his best year came last season when he bagged 15 goals.

It’s a similar story for Scott Hogan who netted 14 times for Brentford last season and is currently struggling to earn a place on the pitch for Aston Villa.

Hogan’s fast-track into the Ireland squad has raised some eyebrows, and Rooney could be forgiven for being frustrated at seeing him leap-frog him in the international reckoning, but he’s maintained a dignified stance throughout the years about his chances for Ireland.

"Everyone wants to play for their country, I’m no different" he said last year. "It would be great if it would happen at some stage. I thrive on scoring and always think that if I get a chance I will take it."

Under O'Neill that chance is looking less and less likely to ever come along. 

Republic of Ireland v Moldova, live on RTÉ2, RTÉ Player and 2fm from 7pm, Live online blog www.rte.ie/sport