The two highly rated Kiwi coaches also traded metaphorical blows at provincial level in New Zealand as recently as 2007, with Crowley at the helm in Taranaki and Gatland back in charge at Waikato.
The pair locked horns again at the Millennium Stadium recently, whilst Crowley was on a fact finding tour of the UK visiting Canadian qualified players, with much mutual respect on show.
"We first met when Warren was a pretty hard uncompromising hooker, performing week in week out for Waikato, they were extremely successful at the time and he was very much a part of all of that," Crowley told the Principality Podcast.
"I also coached against him fairly recently when he was back with Waikato for a couple of years and with Warren you know you are always going to get attention to detail and a positive game out of his sides.
"I'm not at all surprised by the success he has had with Wales. You put systems in place as a coach and if you get buy in, you get results and he is a person who pays the correct attention to that sort of thing so obviously results were going to follow.
"He was great for Waikato, as he has been elsewhere, and New Zealand's loss is very much to Wales' gain at the moment."
Gatland's side take on a Canadian team also set to face Scotland and Ireland on their European tour and the fixture is sandwiched between back to back meetings with the World Champion Springboks and Tri-Nations victors New Zealand.
Whatever happens against South Africa, the Friday night clash with the Cannucks will be Wales' last chance to fine tune preparations for the sell-out meeting with the All Blacks the following week.
And Crowley is hoping his side can rise to the challenge of what he refers to as the impressive atmosphere of the Millennium Stadium.
"Standing here just over a month before we are going to play you really get the sense that it is going to be a huge occasion," said Crowley.
"It's a pretty impressive place and the experience of measuring ourselves against the 6 Nations Champions in their own back yard will be huge, but hopefully we will do ourselves proud.
"The prospect of playing Wales in front of their home fans is what international rugby is all about and we need to find out how we can perform under that kind of scrutiny in that sort of atmosphere.
"Canada is a huge country, I took over in April and some of the distances you have to travel to see players are a real test.
It's a nine hour flight from one end of the country to the other and three-quarters of the sides don't play in the winter because of all the snow, but those are the challenges.
"The side is getting better and better and we are coming to Wales, Scotland and Ireland knowing we have a huge challenge ahead of us but looking to play and do ourselves proud."
Fans can find out what happens when Crowley and Gatland are re-united in international competition 20 years after they first met as All-blacks at the special Friday night Invesco Perpetual Series fixture which has been priced for a family audience.
A family of four can watch the game for as little as £50 with tickets still available online at www.wru.co.uk or from the WRU ticket hotline 08705 582 582 and Gatland is relishing the opportunity to return to the scene of his euphoric 2008 Grand Slam clinching victory over France.
"For any coach preparing an international team is the ultimate, especially when you are running out in front of your home crowd and there is nothing better for me that I've experienced," said Gatland.
"Our last game at the Millennium Stadium was the Grand Slam victory over France and that was a pretty special day.
"I've certainly had a huge buzz from that occasion throughout the last 6 months and hopefully that can continue throughout the Autumn as the expectation of the nation will be on us.
"We are hoping for good support against Canada, I know the WRU are very much setting up the game as a family day out and it will be a great chance for people who haven't been able to pick up tickets so far to come along and support Wales.
"We will approach the campaign in a similar way to the 6 Nations last year, we won't have a large squad, probably just 27 or 28 players and we will keep it quite tight.
"You want all the players to feel like they've got a chance to impress and get game time and we will probably rotate the team and a few positions during the series, but the core of the squad will remain consistent.
"We will be going out to target every game and perform particularly as we are at home, we will be wanting to give a good account of ourselves."
And Gatland admits the chance to catch up with an old foe and colleague in Crowley will add extra spice to his meeting with the Cannucks.
"We were lucky enough to experience a couple of All Blacks tours together and also coached against each other in New Zealand," added Gatland.
"His nickname in the squad was Colt, because he was just a baby when he was first selected, but he was very much a senior figure when I arrived and I learnt a lot from him.
"He's taken a big step to travel round the other side of the world to coach which is another thing we have in common and we must be careful not to under-estimate him and his team.
"If you underestimate a team that's when you get caught, they have a lot of ability in their squad and they come very close to upsetting a few teams in the past so we have to ensure we prepare properly and remain focussed."