The Spaniard scored 18 goals in his debut season in the English top-flight and quickly established himself as a fan favourite. However, his second season yielded just two goals and he was loaned to Napoli the subsequent summer, before eventually returning to Spain on a free transfer.
Shelvey feels it was the arrival of Wilfried Bony that curtailed Michu's stellar form, despite the Spaniard's quality.
“When I signed I think [Michu] was their sort of main guy, in terms of goals and that,” Shelvey said on The Beautiful Game podcast. “Then a week after I signed Wilfried Bony signed. I think personally that sort of knocked the stuffing out of him, because Wilfried came in on a big deal and as the main striker and after that it didn’t really work out for Michu.
“I only played with him for about six or seven months, but you could tell his finishing was just ridiculous.”
Shelvey also revealed how little Michu was sleeping during the forward's dismal second season - a potential explanation for the dramatic drop-off in form from a talented player.
“We had these bands to wear, for when you go to sleep," Shelvey continued. "They monitor you to show how much you are sleeping.
“They put it all up on a screen in the canteen. We had a meeting, there were a few lads going to bed at like 12 and that, on one graph he showed that someone was sleeping for three hours a night, and it was Michu.
“He was coming in and his eyes were drowsy and puffy, it turned out he was just up playing PlayStation til like 4 o’clock in the morning.
“I don’t know if had always been like that. He looked tired all the time, then he got a bad injury. I don’t even know what he’s doing now, he sort of disappeared off the face of the earth, but when he was at Swansea he got a Spain call-up, he played for Spain, and you don’t get Spanish call-ups if you can’t play football.”