The 29-year-old Spaniard, who endured a torrid season-long loan at Napoli last term, is not required to train with the club during pre-season, which started on Wednesday.
Michu is expected to leave the club and it marks a steady decline for a player who scored 22 goals in all competitions for the Swans during the 2012-13 season.
He struggled for injury and form in 2013-14 and then opted for the challenge under Rafa Benitez last season but failed to score in just five appearances in Serie A.
Swansea manager Garry Monk previously stated in May: “Michu is still a Swansea City player and we have obviously monitored his progress there and how he’s got on.
“What I’ve tried to do with that situation is just allow him to concentrate on his football where he is. That was the decision that both of us took in the summer.
“I’ll sit down with him as soon as the season finishes and I’ll speak to him then about his future, and how best to go about it for himself and the future of the club.”