Ronald Koeman is extra harsh on the Spaniard in training.
Sky Sports report that the summer signing cost Southampton a fee in the region of £5 million, his release clause at his former club, and that looked a bargain.
The 22-year-old had recently made his international debut for Spain and Southampton looked to have snapped up a winner.
But so far he has not made a massive impact at St Mary's.
Juanmi has played just 27 minutes of Premier League football and his manager Ronald Koeman has now suggested why.
Speaking to the club website the Dutchman made it clear that Juanmi was yet to adapt to English football - in particular the practice of staying on his feet:
“I don’t say the Premier League is stronger than the Spanish competition, but it’s different in tempo and physically what you need. That needs time.
“We speak with Juanmi about that and sometimes I am the referee if we play a game on the pitch and I don’t whistle.
“I don’t whistle because sometimes he’s falling too easy. He needs to be stronger. That we are trying to develop.
“It’s true (he doesn’t like my refereeing), because we have enough physical strong players and to show what happens in the game you need to change that.”
Of course Juanmi will be hoping for a chance this evening. Southampton are in Capital One Cup action against Aston Villa this evening and several fringe players are likely to be thrown into the action by Koeman.
Juanmi will hope to show he has toughened up enough to get regular Premier League action under his belt this campaign.