Popstar Zayn, 22, left the One Direction World Tour in the Philippines yesterday after being signed off with stress, and flew home to the UK to recuperate.
No further details were given.
Speaking to BBC Newsbeat, singer Sinitta – who works on X Factor and is close friends with 1D's mentor Simon Cowell - suggested Zayn was feeling "burned out" and needed rest and relaxation.
She said: "When we don't see them here, it's not that they're resting, it's that they're in another country. They're literally promoting their records non-stop around the world, so they don't get a lot of downtime."
Sinitta also said it wasn't management pushing the boys, they themselves wanted to be everywhere and make sure every fan was happy.
Of course, the fact Zayn's flown back to the UK and left his bandmates in the Philippines has prompted speculation he could quit 1D altogether...
However, management have said he's hoping to be better in time for their Cape Town concert on 28 March.
So far, he's scheduled to miss two concerts in Manila, Philippines, and one in Jakarta, Indonesia. Harry Styles, Niall Horan, Liam Payne and Louis Tomlinson will continue on those dates without him.
Zayn hasn't tweeted since the announcement was made.
His last tweet, on 18 March, was a declaration of love for girlfriend Perrie Edwards from Little Mix, after pictures surfaced of him holding hands with another woman.
He said: "I'm 22 years old... I love a girl named Perrie Edwards. And there's a lot of jealous f**ks in this world I'm sorry for what it looks like x."
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