Conor McGregor was ready for Dustin Poirier's calf kicks - but was taken aback by their ferocity.
Poirier left McGregor's front leg battered and bruised on his way to stopping the Irishman in the second round at UFC 257.
The Irishman struggled to defend against the tactic and eventually suffered the first KO loss of his career.
And his head coach John Kavanagh admits he was surprised by how effect Poirier's kicks were.
"He does so much sparring that you hope there's not going to be ring rust because hes getting the rounds in," he told ESPN.
"This particular technique is almost impossible to replicate, the fact that Dustin threw it is not that surprising but how devastating a technique it is somewhat that caught us out.
"In the gym, you're not going to kick your partner as hard as you possibly can and you're also both wearing shin pads.
"You can build up a false confidence with that and it's only in fighting you have no shin pads."
McGregor won the first round against Poirier but was soon in trouble in the second round.
He later blamed his inactivity for the loss having spent just 40 seconds in the cage since October 2018.
But Kavanagh insists his star pupil had never looked better during training camp.
"I've never seen him as dedicated or as motivated or training with such intensity for a long period of time," he added.
"He was ticking along for a year but his fight camp training started six months ago and that's more than he's ever done for his career."
Kavanagh confirmed McGregor wants a trilogy bout with Poirier as soon as May - and wants the lightweight title to be on the line.
McGregor won his first fight with Poirier when he knocked him out in 2014 and wants a rubber match as soon as possible.
