Christian Horner has shared his memories and emotions from when Sebastian Vettel left Red Bull to move to Ferrari.
The Red Bull Team Principal is one of many high-profile F1 figures to have shared recollections of Vettel, who recently announced that he will retire from F1 racing at the end of the season.
Horner and Vettel enjoyed a long working relationship in the sport; Vettel joined F1 in 2006 as a Red Bull junior and worked his way up to a Red Bull drive by 2009.
He took his four Drivers' Championship titles at Red Bull, spanning 2010-2013, before a difficult 2014 season triggered his departure from the team.
Horner recalled the circumstances surrounding Vettel's Red Bull exit, and his emotions at the time.
"We weren't in a competitive position at that time," Horner told Sky Sports F1.
"Mercedes had a massive advantage, Ferrari looked like they were on the ascendancy and Renault didn't look like they were going to get themselves sorted out anytime soon.
"We couldn't compete with it, and it was the right thing at that point in time for him.
"He had the desire to follow in the footsteps of Michael Schumacher and the lure of Ferrari – at a time when we couldn't offer a competitive car – was understandable.
"It was sad, but fully understandable."
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Horner heaps praise on outgoing Vettel
In one of the most formidable partnerships in Formula 1 history, Vettel took 38 victories for Red Bull during their period of domination from 2010 to 2013.
He secured Red Bull's first Drivers' Championship success and became the youngest driver to secure consecutive titles, among other records.
Horner continued to recall the qualities that made Vettel a success in the sport.
"On one hand, it was sad to see that [retirement] announcement, but on the other I think the timing is right for him," added Horner.
"He was a massive part of our team. He was a pleasure to work with. He was committed, he was unrelenting in his pursuit of performance, probably the hardest working driver I've ever come across, and beyond that just a really nice guy.
"We had so many special moments, including those four World Championships.
"What he's achieved is quite outstanding, and I just wish him all the very best, hopefully for a safe and enjoyable last [set of] races in the sport."
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