The Tottenham vice-captain is becoming a more and more popular choice to replace De Gea, and there is good reason for that. He has plenty of experience in the Premier League and turned out for former club Lyon in the Champions League.
Spurs will not want to part with the French international who is contracted until 2019, but the 28-year-old may be tempted by a move to Old Trafford.
In one sense Valdes appears to be the most logical option, after all he is already at United, but despite all of his experience he does present a big risk for Van Gaal.
The Spaniard's experience and talent cannot be questioned, but has not played regularly in more than a year, and at the age of 33 there is no certainty that he would be able to find his best form.
After a season warming the bench at Stamford Bridge as Thibaut Courtois' understudy it seems all but certain that Cech will leave the Blues at the end of the season. With four Premier League winners' medals to go with a Champions League title, Cech has what it takes to help United reach the next level.
However, the small matter of Jose Mourinho may derail any potential move. With the Red Devils rebuilding phase stepping up a gear, it would seem unlikely that Mourinho would allow Cech to join a top-four rival.
The Inter Milan shot-stopper is a top performer which experience both in Europe and on the international stage with Slovenia. He's widely tipped to leave Inter at the end of the current campaign.
Handanovic's lack of experience in England certainly shouldn't count against him, he's a quality campaigner and at the age of 30 he should be well placed to make the transition.
It's not the first time that Begovic has been linked with United, the Stoke 'keeper was named as a potential replacement for De Gea when questions where being raised about whether the Spaniard was up to standard (United fans, that wasn't long ago…).
A strong campaigner for the Potters, Begovic might be allowed to leave the Britannia Stadium without too much resistance due to the presence of talented youngster Jack Butland on the bench.
Should Newcastle be relegated you can be sure that the Dutchman will not be looking to spend a season in the Championship. Even if the Magpies do retain their Premier League status, you wouldn't blame Krul if he has become a bit disillusioned with life in the North-East.
Van Gaal knows Krul well due to the time they spent together with the Dutch national team, and as such the United boss will be better placed than most to decide whether Krul can overcome the inconsistency that has slipped into his game in recent times. The 27-year-old set the Premier League alight when he first established himself as a Newcastle regular, and if he can regain that form he may be what United need.
Currently warming the bench at Real Madrid, Navas' game-time will likely be reduced even further if De Gea makes the move to The Bernabeu.
The Costa Rica international is surely too talented to be relegated to the replacements week in and week out, but whether he is deemed good enough for United is less certain.
The 22-year-old Perin would certainly fall into the 'outside bet' category. The Genoa 'keeper has been very impressive in this season's Serie A and is thought of by many as one of the best young goalkeepers in Europe.
If United agree a player plus cash deal for De Gea it seems unlikely that they would look for Casillas to be the make-weight in the deal, with a certain Welshman in their sights. While Casillas is no longer at the height of his powers, a move away from Madrid could work wonders for the Spanish international.