Swansea announced on Monday the 29-year-old forward's contract, which was due to expire at the end of this season, had been rescinded by mutual consent.
Michu, who netted 22 goals in all competitions during his first season at the Liberty Stadium, winning the 2012-13 League Cup in the process, has struggled badly for form and fitness in recent years due to a long-running ankle injury.
He initially underwent surgery in December 2013 and spent last season on loan at Napoli, where he made just three Serie A appearances, two of them starts, and failed to score.
The one-cap Spain international trained with Langreo, who are coached by his brother Hernan Perez, in the off-season before requiring further surgery.
"He has suffered terribly. Many people would have thrown in the towel already," Perez told Radio Marca.
"[The psychological] element is possibly what we have to work on. It's not that he's in a bad way, but it is true that he has gone from being a professional footballer to finding that interrupted now for almost two years.
"He has to reconnect, feel like a sportsman again, feel useful, feel healthy. He's a strong guy and in very little time I think he will be at 100 per cent of his mental capacity too.
"Hopefully he can get back to being what he was; we are going to help him."
According to The Guardian, Michu could make his Langreo debut against Caudal on Saturday, if he receives international transfer clearance in time.
Perez believes his brother is still able to earn a regular place with a top-flight club, revealing the former Rayo Vallecano man, who scored 15 Liga goals in 2011-12 to earn his move to Swansea, turned down several approaches in the off-season as he sought to regain full fitness.
"I hope that in a few months' time he is back playing at a higher level. If in three or four months' time he is fine, if his ankle responds, if he recovers that muscle and if emotionally he is fine, and a first division club comes, then [he can play in] the first division.
"There were offers [in the off-season] and many people would have signed the first contract that came along and if you can play, but he is very honourable and he did not want to sign with anyone until he was 100 per cent fit. You can't con people."