And the 25-year-old wing/centre from Oakville, Ont., is fitting in nicely in the top level of English rugby, having scored two tries already for the newly promoted club.
The latest came last Sunday in a 29-19 loss to London Irish. The Canadian also scored in a 28-23 loss to Saracens on Oct. 7.
London Welsh (2-5-0) currently stand 10th in the 12-team Aviva Premiership.
There have been drubbings at the hands of champion Harlequins (40-3) and perennial powerhouse Leicester (38-13) but otherwise the Exiles have kept things closer in the league.
"I've loved every minute of it, to be honest," Mackenzie told The Canadian Press. "It's a great atmosphere here and the chance to play at the highest level week in and week out is what I've always wanted. I'm a very happy camper."
The six-foot-one, 213-pound MacKenzie worked his way up the English rugby ranks, playing first for Coventry and then Esher in the second-tier Championship. He scored 12 tries for Esher last season when he was named the team's player of the year by both his teammates and club supporters.
"The Championship's a really good standard of rugby but I knew that the finer things mattered a lot more in the Premiership, as in the little details of the game. And those are the things that you've really got to focus on.
"That's been really good. I think I've been improving week in and week out with the coaching stuff we've got here. And the chance to play against some of the best players in the world every week is ideal."
"Seems like every weekend you're up against a world-beater," said Mackenzie.
Fellow Canadian Jebb Sinclair is also in the Premiership although he has been in South Africa most recently after London Irish loaned the forward to the Stormers and then Western Province.
"I actually hung out with Jebb a lot last year because he was just down the road from me," said Mackenzie. "So I understood what he was kind of up to and how things were going for him at Irish."
Cracking a Premiership team isn't easy for foreigners. Teams are restricted to two imports on the pitch at any one time.
Players from European Union countries don't count as foreigners. Neither do South Africans, thanks to a deal between the two countries' rugby unions.
Players with EU spouses also avoid the import restrictions.
Mackenzie plays his games at Kassam Stadium in Oxford, home of the Oxford United soccer team. His club trains at its longtime home of Old Deer Park in Richmond in suburban London.
With London Welsh, Mackenzie has got the chance to line up with mercurial Welsh international Gavin Henson who has made headlines on and off the rugby field.
At 30, the former International Rugby Board's Young Player of the Year is on his seventh club team. Away from rugby, Henson was engaged to singer Charlotte Church and made appearances on several reality TV shows, from dancing to dating.
"On the pitch I think you always knew he was capable of almost anything. He put in a great pass against Sarries (Saracens) for us to score a really good try a couple of weeks ago that not many players would have been able to do," said Mackenzie.
"He's one of the hardest-working guys here. There's only positive things to say about him."
On the international level, Mackenzie made his debut for Canada in 2008 against Portugal and has won 13 caps, including four at the 2011 World Cup in New Zealand.
He scored twice for Canada at the tournament, standing out also for his orange boots and dyed blond hair.
These days Mackenzie is sporting lime green boots.
"You always need bright boots as a winger," he said cheerfully. "You've got to, it's a prerequisite.
"And then I actually cut my hair recently. I finally got the blond out of it so I just have a high and tight haircut right now with no colour, which is a little boring but we'll see what happens in the future."
Mackenzie is part of the Canadian team slated to play against Samoa, Russia and the New Zealand Maori in November in England.
His younger brother Jamie was also a member of Canada's World Cup team, one of 13 sets of brothers who competed at the tournament.
Jamie, 23, is currently playing club rugby in Victoria and focusing on finishing his university degree.
London Welsh hosts Bath (4-3-0) on Sunday.