"We get on well and we've started giving a bit of banter.
"After winning in London he leaned over and said he'd beat me at Rio (in the 2016 Paralympics in Brazil) so I just told him to look at the clock (and Leslie's world record time) and good luck.
"We're getting a good, friendly rivalry going and that's got to be good for both of us."
He doesn't expect his world record to fall in Montreal though as his training has been focused on "winning and not the time" and he's confident he'll do just that, despite Sanchez's eagerness to usurp his crown.
"I've been doing a lot of training, but probably not at the level I would be happy with normally or if it was (leading up to the) Paralympics. But I've been in Australia recently for some training and that went really well so I'm confident," Leslie said.
"The training hasn't been about focusing on records though, It's been about training the body and mind to be fresh for the next three years of training for Rio 2016.
"There's going to be a lot of sacrifices over that time so this year has been to enjoy some of the things I haven't been able to enjoy in the lead up to London."
He also thinks he's a good chance for a medal in the 50m backstroke, saying it would be down to how good a start and break out he got.
"I've been working on the 50m backstroke for the last two or three years.
"It's bit slap and dash and things have got to go my way to get a medal, but you've got to be in to win."
Leslie said part of his job at the championships will be to help mentor some of the younger swimmers coming into the squad for the first time.
"Part of my role is to take them under my wing and teach them about swimming at a championships like this and a lot about the mental side of things. For young, fresh swimmers that's one of the hardest parts to deal with."
But those youngsters don't include 15-year-old Bay of Island's swimmer Daniel Gaualofa, who met the qualification standard set by Paralympics New Zealand for the biennial world champs.
"Daniel will be there in years to come though," Leslie predicted.