When Thibaut Courtois joined Real Madrid from Chelsea, the possibility of David De Gea ever moving to the Santiago Bernabeu seemed over.

His chance had come and gone. That night in 2015—the one when a dodgy fax machine was blamed for failing to document the terms of a £29.3 million move from Old Trafford—would forever leave us wondering how he would have fared in Madrid colours.

Yet here we are, seven months on from a £35 million deal that took Belgium international Courtois to the Santiago Bernabeu Stadium, and De Gea is once again being linked to them, per John Richardson of the Sunday Mirror.

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There are many rumours swirling around the Spanish capital now that Zinedine Zidane is back in charge, but could a move as significant as this really be one of his priorities?

Sources in Spain have been convinced since Zidane returned that it could bring a premature end to Courtois' stay. They cited his admiration for Keylor Navas as one reason, but also that the Madrid manager had not shown much interest in the former Chelsea No. 1 becoming his first-choice goalkeeper in the past.

So now we head towards another summer wondering if De Gea is going to be targeted once more.

The Spain international has still not agreed terms on a new Manchester United contract and, with his current deal set to expire in 2020, it opens up the possibility of negotiations with other clubs if it remains unresolved next season. 

If De Gea does make the move, it would have a knock-on effect for some of the game's other top goalkeepers.

Would De Gea Make The Move?

With United still stuttering over an agreement to put their No. 1 on the same terms as Paul Pogba and Alexis Sanchez as the club's highest earners, De Gea is in limbo.

The 28-year-old would sign if the club showed he is as valuable to them as the big-name outfield players, but right now there are signals that Madrid would be able to sign him.

It's the only club in the world De Gea is still tempted to join, according to United sources, and there is a growing fear around Old Trafford that Zidane's arrival may mean a bid is on the table soon.

Despite his contract ending next year, United would demand close to £100 million for him—taking their lead from Chelsea and star player Eden Hazard's situation. Indications from Spain suggest they would not pay more than £70 million.

United are still striving to satisfy De Gea's salary expectations and know he would be a huge loss, but there is also a belief that Madrid are more focused on signing outfield players, which could help them out.

How Would United Replace De Gea?

United have been building a list of potential replacements over the past two years due to the fragile situation with De Gea.

Three names that have predominantly led their focus are Atletico Madrid's Jan Oblak, Kasper Schmeichel of Leicester City and Jordan Pickford of Everton and England.

One source told Bleacher Report that Pickford has dropped behind the others due to his form over the past season, but Schmeichel is extremely keen to push his career to the next step and would not be fazed by the prospect of guarding the same net his father, Peter, once did.

Oblak is a name that creates real intrigue, though. One insider explained: "He is the only 'keeper—apart from Marc-Andre ter Stegen—that the club believe can be considered alongside De Gea right now as the best in the world."   

Oblak has had his own contract talks dragging on with Atleti, but according to Isaac Suarez of Marca, he has a new deal agreed in principle that would make him the side's second-highest earner behind Antoine Griezmann.

Could Courtois Ever Return to Atletico Madrid?

Navas took over the gloves for Zidane's first game back in charge of Los Blancos, and Courtois is now in a frustrating and awkward situation.

One of the main reasons he pushed for the transfer from Chelsea to Madrid was to become a crucial part of the side while also being close to his children, who continued to live with their mother when he moved to Stamford Bridge. Any further decisions over his future would undoubtedly work around that same important factor.

Courtois was previously on loan at Atletico Madrid, so a return would seem ideal. However, the situation is complicated by the fact that supporters are furious with the way he left for Chelsea and then returned to join their city rivals. They even threw toy rats at him when he played against them recently.

Interestingly, though, informed sources have told B/R that Atletico manager Diego Simeone remains a great admirer. By selling Oblak and taking Courtois, they could even make money on the deal.

It's a long shot, though, and if Atletico are not willing to risk a backlash from supporters, a switch to Paris Saint-Germain—as a long-term replacement for Gianluigi Buffon—might be his only option.

De Gea's situation is complex, and moving to Madrid is far more difficult than just an agreement between two teams.

The impact on Oblak and Courtois should give United more time to strike a deal with the goalkeeper they already regard as the best in the business.