McCarthy said: "Our team doctor Alan Byrne has spoken to the Brighton medical team and had a look at the scans.

"The scans have confirmed the groin injury and Aaron won't be ready in time for New Zealand and Denmark."

The teenager's absence represents a significant blow to McCarthy despite the return to fitness of Sheffield United striker David McGoldrick, who sat out last month's qualifiers against the Georgians and Switzerland through injury.

Connolly produced a thrilling late cameo in Tbilisi and very nearly won a tight encounter, in the process earning himself a first senior start in Geneva three days later.

McCarthy has opted not to call up a replacement with Callum Robinson, James Collins, Scott Hogan and 17-year-old Tottenham striker Troy Parrott already in camp.

McCarthy is wrapping star men Darren Randolph and McGoldrick in cotton wool ahead of the crunch clash with Denmark.

Ever-present goalkeeper Randolph returned to action for club Middlesbrough in Saturday's 2-2 Sky Bet Championship draw at QPR after three games on the sidelines with a thigh injury, while Blades forward McGoldrick – who missed last month's qualifiers in Georgia and Switzerland with a groin problem – is just four appearances into his comeback.

Neither man is likely to play any significant part in Thursday evening's friendly against New Zealand as a result, with McCarthy indicating he would be happy to start Randolph against the Danes on Monday even if he does not train this week.

He said: "David has come back, he's had two or three games back and he's been playing well for Sheffield United – and how the hell his goal was disallowed on Saturday is beyond me, by the way. That's another matter.

"I'm delighted to have him back. Darren Randolph, we'll have to look after him because he only came back on Saturday.

"It's other players, players like Robbie Brady, who's not been injured, but then had one game, and then he's had two or three minutes since, so it's kind of difficult balancing it between those who are playing and those who are not.

"But Robbie at least is back and he's been back in the squad for Burnley."

The Republic collected just a single point from last month's fixtures in Tbilisi and Geneva to leave themselves needing to beat Denmark to secure an automatic qualification spot barring an unlikely series of events elsewhere.

Had McGoldrick, who scored a priceless late equaliser against the Swiss in Dublin in September, been available, things might have been different and McCarthy has acknowledged that – despite the emergence of Connolly – he was missed.

He said: "I would always prefer to have my best players playing, and he has been our stand-out centre-forward, so any team of any ilk, any stature would miss a player like him, especially how he was playing, and he was loving it.

"The goal he scored against Switzerland, of course, I think everybody loved him for that."

McCarthy intends to pick a team for Thursday night which will not impinge upon Monday's game with the likes of 17-year-old Parrott, Celtic full-back Lee O'Connor, Shamrock Rovers midfielder Jack Byrne and in-form Newcastle defender Ciaran Clark likely to get game time.

He said: "There is scope for them to do themselves a whole lot of good. Whether that transmits into Monday, let's find out.

"Let them get in and play well, let's hope they play well and we win and let's see how I feel about them after the game."