The 21-year-old made the move to Celtic from MK Dons for £1.5million. It is a transfer fee that still provokes a disbelieving shake of the head and likely plenty of laughter around the recruitment office of the Scottish champions.
He ended up in Milton Keynes following a training stint with the club after turning down a new offer at Fulham. On confirming his arrival, MK Dons noted O’Riley had “attracted interest from the likes of Liverpool, Borussia Dortmund and Manchester City during his young career".
Former Scotland and Rangers centre-back Russell Martin was the manager at the time.
He said: “We all recognised, very quickly, what a gifted footballer he is and why he’s been wanted by some big clubs over the last few years.”
Clubs sent scouts to watch him in England’s third tier, such an unfashionable league for such a polished and sophisticated footballer. Those clubs, in the Championship and Premier League, recognised the talent but it is understood there were some doubts about the ability to step up to that level at his age. Nothing to do with his technical qualities but whether he would be able to combine those with the physicality and pace required to operate at the top.
Safe to say, it was a misstep which Celtic, to their credit, took full advantage of.
Premier League interest
The stats from his time at MK Dons backed up why Ange Postecoglou and the recruitment team were so keen. He is the poster boy of what Celtic want to do in the transfer window. Unearth these gems who have been overlooked, give them a platform to showcase their talents with a view of making a sizeable profit after they have helped the club gain success.
If a club was to approach the league leaders in January with their chequebook open, they may well have to write a figure that is ten times what Celtic paid back in January.
Newcastle United have taken an interest in O’Riley. They have eyes therefore it is completely understandable why they are keen. According to the Scottish Sun, the Magpies had him watched in action for Denmark Under-21s, scoring in a play-off clash with Croatia.
The midfielder has spoken previously of interest from Newcastle United as well as Leicester City.
“It didn't matter that any of them made an offer. If there is no offer, then it is not very concrete in my head.
"I didn't really think about it because nobody from Celtic told me that, for example, Newcastle had made an offer. It wasn't like that so there wasn't much to think about.”
It’s almost as if Premier League clubs have been waiting for someone else to take the plunge with O’Riley, weigh up how he adapts to a higher level and then make their move. A curious if somewhat expected approach.
O’Riley is the real deal.
He has become a key part of Ange Postecoglou’s midfield alongside Callum McGregor and Reo Hatate. A recent study revealed him to be the most creative player in the Scottish Premiership this campaign. No player has provided more assists or created more big chances than the 21-year-old.
The way he can operate on the half-turn, taking possession in tight areas against defences in a low block while providing expert penetration is unrivalled in the Premiership when it comes to midfielders. And it is not just domestically, he demonstrated that in the first-half of Celtic's Champions League match with Real Madrid.
It is that side of the game which is unlikely to surprise interested parties.
World Cup on the horizon
Out of possession, the defensive side of the game, he has been effective and productive. The way Postecoglou wants to play, the team can't carry passengers out of possession. O’Riley plays on the right of a midfield three. He is required to cover out wide, combining with Liel Abada and Josip Juranovic in preventing any forays from opponents down Celtic’s right.
Just the eye test is enough. O’Riley is an athletic 6ft 2in creative midfielder who is mobile. He averages 2.82 interceptions per 90 minutes in the league and wins the ball back more than six times per 90 minutes. Solid numbers for an attacking midfielder in a team which dominates possession.
He is a player who should be enjoyed, by Celtic fans and neutrals, and one who will likely continue to attract attention, while a full cap for Denmark is surely on the horizon with a possible chance of appearing for the country at the World Cup later this year.
The good news for fans of the Scottish champions, he doesn’t appear to be in any rush to up sticks and return to England.
"It's great to get some recognition because it means I'm playing well at Celtic,” he said earlier this month.
"As I say, Celtic is the perfect place for me right now. It's a big club. We play in the Champions League, the fans are insanely good and the team is good.
"It's the perfect place to be and I also think it's a good place to be if I want to go to the World Cup with Denmark."
Ultimately, indecision from clubs in England has allowed Celtic to take advantage of the situation and mould a midfield three which creates and controls but can compete physically.