KSI left Tommy Fury in disbelief after a bold claim about his brother Tyson – before fans accused him of knowing "nothing about boxing".
The celebrity boxing stars clash in a massive Battle of Britain bout on October 14 in Manchester.
And before the DAZN pay-per-view showdown the two sat down for a heated face to face interview.
Tommy was quick to bring up the fact he regularly spars with his older heavyweight champion brother Tyson.
He said: "I've been getting hit off him my whole life. So what makes you think you can do something to me?"
To which KSI responded: "Tyson doesn't hit hard like people like [Deontay] Wilder and s*** like that."
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Tommy – who watched twice as Tyson knocked out Wilder – was left head in hands in shock.
He said: "Who knocked out Wilder? Tyson knocked him out. Tyson knocked him out, this proves they don't know boxing."
Fans seemed to agree with Tommy as one reacted: "Tommy Fury PROVES KSI Knows NOTHING About Boxing."
Another added, noticing KSI's face after he said it, added: "Yeah that’s wild from KSI I won’t lie. But cringe as well.."
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