The signing has already sparked questions to Louis van Gaal's motives; is the Dutch coach just interested in providing competition to his sparkling young No 1 David De Gea, or is Valdes a replacement for his fellow Spaniard with Real Madrid interested?
Valdes has been out of contract in June, when Barcelona let his contract expire after 12 years as the No 1, where he won six La Liga titles, two Copa Del Rey trophies and the Champions League three times.
In a dominant era of football for Barcelona, Valdes was sometimes pointed to as a weakness, but the 32-year-old rarely let the side down when teams managed to wrestle the ball of Lionel Messi, Xavi and Andres Iniesta and have a chance of their own.
Indeed, a poor player doesn't rack up 535 appearances for a club team seen by many as the best ever.
Valdes' main criticism was that he was not dominant from crosses but he stands only 6ft, while Barcelona's high pressing style meant that when he did face the opposition he was in one-on-one situations.
At international level he only won 20 caps, mostly in friendlies, but was unlucky to have Iker Casillas in front of him for much of his career.
Valdes is only a free agent now because of the knee injury - tearing his ACL - suffered in March. Valdes had agreed a contract with Ligue 1 side Monaco, but the club refused to sign him after learning of the extend of his injury. If fit, Valdes would likely be the Monaco No 1, ahead of Croatian Danijel Subasic.
Louis van Gaal offered him the chance to recover from his injury at their state of the art Carrington complex and, according to the Daily Mail, has so impressed Van Gaal that the Dutchman has decided to offer him a contract.
David De Gea is in absolutely sparkling form and is arguably the best goalkeeper in the Premier League at the moment. But rumours of a return to Spain and Real Madrid won't go away. Iker Casillas is a shadow of his former self and Los Blancos are actively looking for a replacement.
De Gea, surrounded by a large group of Spanish speaking players at Old Trafford and a sworn Atletico fan, isn't the most obvious candidate for Real (Petr Cech would likely be more willing to join) but a return to his homeland, and Spain's biggest club, may be too much to turn down.
Whatever the true intentions of Van Gaal, it is certainly a shrewd move. If De Gea stays then United suddenly have a new No 2 that is an upgrade over Anders Lindegaard, who can provide real competition to De Gea and, hopefully, spur him on to better things or step into the breach if De Gea falters.
If De Gea chooses to leave for Real Madrid then Van Gaal has an experienced goalkeeper who would start for many clubs across Europe. He could provide the perfect stop-gap as United search for their next No 1.
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