Kyle Gilmour and Adam Kleeberger have been ruled out of the tournament by medical staff, but John has asserted the strength of new charges Tyler Ardron and Sean White.
"We are always looking to develop players and sometimes circumstances require you to bring new players into the fold, like Tyler Ardron, who is yet to represent Canada on the international sevens circuit," John said. "But Tyler is fit and athletic and very good on the restart. He shows great potential in sevens.
"Sean White has played at scrum half and hooker on the international sevens circuit for Canada and he has just returned from the Rugby World Cup, so we're confident in our replacements."
Gilmour suffered a broken arm during a club game for St. Alberts in Alberta, while medical staff advised Kleeberger a further week of rest was necessary following a demanding Rugby World Cup in which he started all four pool games for Canada.
"When Adam finally got back to Canada, he was physically and mentally exhausted from the tournament," John said. "We discussed with the medical staff and they felt it was best he had another seven days off."
Canada will face U.S.A, Brazil and Chile in the pool stage of the tournament. Following that, the pools cross over, with first place in Pool A playing fourth in Pool B and second crossing over to play third, to begin the knockout stages.
The other pool consists of Argentina, Uruguay, Guyana and Mexico.
The team departs Canada for Gudalajara Friday and will have a week to prepare for the tournament and acclimatize to the altitude and heat.
Regardless of the late changes, John and his team head to the tournament with belief in their ability to make a statement in Gudalajara.
"The games will be hard but we're going in with a genuine chance of winning it," John said. "We've got a lot of speed with guys like Conor Trainor, Matt Evans, Ciaran Hearn, Sean Duke and Taylor Paris. We've got speed, power and experience."
The Pan American games, which features international teams from all around the Americas zone, is integral to both the development of Sevens, for both the sport and the Canadian team, in preparation for Olympic inclusion in Rio de Janiero in 2016.
The tournament began in 1951 and is held every four years. The 2011 fixture sees Canada send its largest contingent of athletes ever, with 493 competitors travelling for the tournament. In total, 6,000 athletes from 42 countries will attend, competing over 39 sports, as part of the qualifying process of the 2012 Summer Olympics in London.
Canada's last Pan American Games performance in 2007 resulted in a third-place finish overall, with a medal tally of 138, including 39 gold.
Toronto will host the next Pan Am Games in 2015.
Canada vs Chile
Canada vs Brazil
Canada vs Argentina
Canadian Sevens Team
Tyler Ardron (Peterborough, ON) (Ontario Blues)
Nanyak Dala (Saskatoon, SK) (Prairie Wolf Pack)
Sean Duke (Vancouver, BC) (British Columbia)
Matt Evans (Duncan, BC) (Unattached)
Ciaran Hearn (Conception Bay, NFLD) (The Rock)
Nathan Hirayama (Richmond, BC) (British Columbia)
Phil Mack (Victoria, BC) (The Rock)
John Moonlight (Pickering, Ontario) (Ontario Blues)
Taylor Paris (Barrie, ON) (Ontario Blues)
Mike Scholz (Oakville, ON) (Ontario Blues)
Conor Trainor (Vancouver, BC) (British Columbia)
Sean White (Victoria, BC) (BC Bears)
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