Last month, Zayn Malik announced he had left One Direction after five years with the boyband, claiming he wants to be a "normal 22-year-old" again.
And while Simon has openly admitted he was shocked by Zayn's departure, the music mogul is confident 1D will continue their success and more as a four piece.
During his appearance on The Late Late Show with James Corden earlier this week, Simon opened up about Zayn's departure and his hopes for 1D going forward.
When asked by host James to recall when he was when he heard the news Zayn had gone, Simon jokingly replied: "About to jump off a cliff..."
He continued: "No, I was in Miami and I kind of knew this was coming if I'm being honest with you. We had a few conversations, he wasn't happy. I was trying to say to him I think he should stay around a bit longer and then something in him just said 'no, I've had enough'."
As much as Simon had tried to persuade the X Factor star to stay with the group, he admitted: "Once someone has made their mind up, they're going to go.
"I didn't want to push him too much, he's 22. I could see he was a bit stressed and needed some time off, so I had to respect his decision."
News of Zayn's exit came as One Direction were busy touring on their 'On The Road Again' tour.
Reassuring fans they would carry on as a four-piece, Harry Styles, Liam Payne, Louis Tomlinson and Niall Horan continued to perform at their tour dates, with Simon insisting the boys put on an incredible show.
"I have to hand it to them," he said, "They were in-credible. To work everything out so quickly, they were amazing."
Insisting he thinks the boys' still have plenty of fuel left in their tank, Simon teased Direction'ers by revealing 1D could soon have a very big hit on their hands.
"I've heard some of the early stuff," he teased. "I have a feeling that this year they're going to make the best record they've ever made."
Well, now we can't wait to hear it, can you?!
Zayn announced he had quit One Direction for good, after being signed off from the band's latest tour with stress.
Apologising to fans in a statement, he said: "My life with One Direction has been more than I could ever have imagined... I'd like to apologise to the fans if I've let anyone down, but I have to do what feels right in my heart."
His bandmates, meanwhile, said they respected Zayn's decision.
"We're really sad to see Zayn go, but we totally respect his decision and send him all our love for the future. The past five years have been beyond amazing, we've gone through so much together, so we will always be friends."
Earlier this week, the first official picture of One Direction as a four piece was released, marking the band's next chapter.
One Direction first rose to fame while starring on the seventh series of The X Factor back in 2010. After auditioning as solo artists, the boys were put together during bootcamp to form a band, going on to finish third in the competition overall.
Since The X Factor, 1D has gone on to sell more than 50million records, bagging themselves three consecutive number one albums in the UK.
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Watch Simon's appearance on The Late Late Show with James Corden here: