The Premier League champions made a late bid for the Argentine but later withdrew their interest, allowing Valencia to close a deal after the window had closed
Goal reported on the eve of the transfer window closing that the Premier League champions had made a late, £12.3 million bid for Porto's Argentina defender.
A deal failed to materialise, however, and rumours surfaced late on January 31 that Otamendi would be moving to Valencia, although the move was not completed until after the deadline passed and he has not been registered to play in La Liga this season.
Otamendi will now go out on loan until the end of the campaign, with the leatest reports suggesting Copa Libertadores champions Atletico Mineiro as his destination, but Rufete says the Primera Division side had to take the opportunity to sign him when they could.
"If I try to buy Otamendi after the World Cup, it's possible he couldn't come," he told a club supporters' lunch.
"A great sacrifice and a lot work was necessary for him to come. He will explain that when he arrives. We saw that Manchester United pulled out and we moved in."
Porto confirmed to the stock exchange that they will receive €12m (£10m) plus bonuses for the centre-back, who has agreed a five-year deal at Mestalla.
Uncertainty still surrounds the deal, however, with reports in Spain suggesting that Otamendi could not complete his move because the club already had a full quota of non-EU players on their books, while it has also been reported that he did not arrive for negotiations before the transfer window closed.
Either way, Otamendi has already spoken to the official Valencia website about the move: “After playing for a club like Porto, a very big prestigious and big one, it is an honour to join Valencia, one of the most historic in Spain and Europe," Otamendi told reporters. "I am very happy for this step in my career."