Middlesbrough stop-gap became irreplaceable at Riverside Stadium: View | OneFootball

Sometimes, a player arrives through the back door of a football club, and leaves with the front door being held open for them.

Dimitrios "Dimi" Konstantopoulos was one such player, as his planned short-term stay evolved into a Middlesbrough career that few goalkeepers have come close to matching in recent times.

The Greek goalkeeper returned to a part of the world he was familiar with in 2013 - having spent time with local neighbours Hartlepool United between 2003-2007 - on a free transfer, after being released by AEK Athens.

Then, 34, Konstantopoulos was brought in to effectively be another pair of hands on the training ground, as young shotstoppers, Jason Steele and Jayson Leutwiler, respectively, were ahead of him in the pecking order.

But through a mixture of fate, and fending off multiple challengers, Dimi would fight his way out of the Rockliffe shadows and into a record-setting spell on Teesside that will never be forgotten.

The sliding door Boro moment that gave Dimi his chance

An injury to Boro's number one goalkeeper, Steele, early in the 2013 season, forced Aitor Karanka to seek the help of another experienced pair of hands. This came in the form of legendary Irish keeper, Shay Given, who arrived on a temporary loan deal from Aston Villa in November.

Despite not being trusted to take the reins, this sequence of events did earn him a promotion to Karanka's matchday squads as the backup, but his big chance was about to come.

As Given returned to Villa Park in late February 2014, Dimi's big break finally arrived, as the Boro boss handed him his Championship debut in a home game against Ipswich Town.

Final day of the season aside, the Thessaloniki-born goalie would go on to start every single one of Middlesbrough's remaining league games in that 2013/14 season.

And it was this slice of fortune that earned him his chance to impress Karanka, and impress he did, as he earned a one-year extension at the end of the season.

What Konstantopoulos achieved over the following two seasons was nothing short of remarkable, as he became one of the best goalkeepers in the second tier.

An unconvincing start to the 2014/15 season by a young Tomas Mejias, left Karanka once again calling on his veteran option to take over as his number one after just a handful of games. This time, however, Dimi didn't feel like giving that position up, as he took the shirt and ran with it from that point forwards.

Dimi's performances during the 2014/15 season - which Boro would lose in the play-off final vs Norwich - ensured that he'd already repaid the manager's trust in him. Boro would finish top of the tree in some of the most important defensive metrics, as the team's 37 goals conceded, 21 clean sheets and an average of just 0.8 goals per game conceded ratio, were all Championship best, per SportsMole.

And if you thought it couldn't get any better, it did. Dimi's exploits in the 2015/16 promotion winning season enabled his defensive unit to write themselves into the Middlesbrough record books.

With Boro's Greek goalkeeping god between the sticks, Boro would set new league records in both consecutive home clean sheets, and consecutive home and away clean sheets, with nine for both categories respectively.

Boro boss attempts to replace the irreplaceable

As Middlesbrough's Premier League promotion celebrations turned to planning for Karanka and his staff, it was - at least for a while - unclear as to whether he would retain faith in the pair of hands that had contributed so heavily to getting the club back in the top flight.

Boro's new fan favourite certainly had his fair share of supporters who let their feelings be known about the prospect of replacements on the horizon, but those efforts were to be in vain, as the club made multiple moves in an attempt to make further upgrades in goal.

Multiple-time Champions League winner and Spanish goalkeeping legend Victor Valdes was the first to arrive, shortly followed by American international Brad Guzan - a keeper with Premier League pedigree to his name also.

These arrivals pushed Konstantopoulos down to the third choice goalkeeper position, and in-turn left his days wearing the Middlesbrough badge numbered, as the Greek would only represent Boro a further eight times between 2016-2019, as per Transfermarkt.

But breaking records was just what he did, and so it felt suitable that he would become Middlesbrough's oldest ever player in an FA Cup tie vs Peterborough in January 2019.

Konstantopoulos' Boro story is one that the Riverside faithful fully engrossed themselves in, as his underdog uprising from training ground helper to Championship record breaker saw him worshiped by those who frequented Teesside's terraces. A true Middlesbrough cult hero.