That would be a world without the NHL's hold on those players. Canada got that luxury last year during the lockout, when defenceman Dougie Hamilton and forwards Jonathan Huberdeau and Ryan Nugent-Hopkins got to participate.
This time around, Canada will hold its selection camp with just one NHL player: Minnesota Wild defenceman Mathew Dumba. While MacKinnon was never a real consideration given his role with the Colorado Avalanche, the Calgary Flames won't release Monahan, the Washington Capitals won't release Wilson and it's highly unlikely the Toronto Maple Leafs let Rielly leave to play in the tournament, which begins Dec. 26 in Malmo, Sweden.
"Every NHL team is a little bit different in how they're set up and how they do things," Canada coach Brent Sutter said. "They look at their rosters, and how significant roles those players are playing on their teams right now. So it's all different. You can't put them all into one, because every organization is a little bit different in how they see their team right now."
In hanging on to Rielly and Wilson, the Leafs and Capitals are making it clear they feel the NHL is a better place for continued development than the world juniors. Hockey Canada has no choice but to accept those decisions, even if management believes the tournament can be a stepping stone.
"This is a real pressure-filled situation, there's a lot of expectations on these young players," Hockey Canada senior director of hockey operations Scott Salmond said on a conference call with reporters. "Any time I think a young player can get that kind of experience on that kind of stage, it's good for their personal development and then hopefully it translates into more success as they return back to the NHL and have that confidence and have that experience."
Dumba, the seventh pick in the 2012 draft, will get that chance after playing in just 13 of the Wild's first 28 games.
But experience can also come from continuing to play in the NHL, which is how the Leafs feel about Rielly. General manager Dave Nonis told Hockey Canada that it was unlikely Rielly would be made available for the world juniors but didn't give completely rule it out in the event that circumstances change with the roster, according to a team spokesman.
For now Rielly is staying in Toronto.
"He can play here and he can make a contribution and he's growing into an NHL hockey player," Toronto coach Randy Carlyle told reporters after Monday's practice. "If we felt we were being counterproductive in his growth or his development, then it would make that decision that much more difficult."
Rielly made the decision difficult to keep him out of training camp by showing he was one of the best seven defencemen the Leafs have. When the blue line is all healthy, he's on the edge between playing and sitting in the press box.
The 19-year-old defenceman has eight assists in 21 games and is 15th among rookies in ice time, averaging 17:43. He has been a healthy scratch six times.
Rielly had a goal and two assists in last year's world junior tournament, when Canada lost in the bronze-medal game. Unable to go this time, it's not because he's not good enough but because he has progressed in his career.
"I think I knew that if I played here this year in Toronto that there'd be a pretty good chance I wouldn't be going over to Europe to play in that tournament," Rielly told reporters Monday. "This is what happens sometimes. I play here, and my priorities are here in Toronto."
Wilson's priorities are in Washington, too, though he's playing far less than Rielly. The big 19-year-old has been on the Capitals' fourth line all season, has a goal and three assists and is averaging 7:10 a game.
That's eighth-lowest among 118 rookies in the NHL this season and 178 fewer minutes than Rielly. But Wilson has appeared in all 27 of Washington's games, and general manager George McPhee said through a team spokesman that the right-winger means too much to the Capitals to leave for the world juniors.
Hockey Canada had been hoping Monahan — currently out with a fractured left foot — would be free to go to the world juniors as part of an unofficial rehab assignment once healthy. The Flames squashed that Tuesday, telling Monahan and Hockey Canada that it wasn't going to happen.
"We have spent a great deal of time discussing and debating the pros and cons of the situation in the context of what is best for Sean’s continued professional development as a hockey player, as well as what is in the best interests of our team, our fans, and our organization," general manager Jay Feaster said in a statement. "We have concluded that in light of the prominent role Sean has played on our team to date, and the role we project he will continue to play once he returns from his injury, that Sean will remain with our hockey club."
As Sutter pointed out, no two organizations feel exactly alike on the subject of prospect development. What Dumba, Rielly, Wilson and Monahan have in common is that their NHL teams all felt they had graduated beyond playing another season at the junior level.
"For me, (Wilson is) an NHL player," Capitals coach Adam Oates told reporters. "He's conquered junior. Nothing against that tournament at all. I think he’s moved past it."
When Rielly was going into camp with the Leafs, Toronto Marlies coach Steve Spott noted that some young players thrive off challenges. Making the NHL was one, but the world juniors represented another chance.
Salmond said other than the Stanley Cup playoffs, there are few opportunities like this tournament. And, of course, there's a benefit for Hockey Canada in having the best players available to it.
"Over the years we've certainly had a lot of discussions on players and what we feel the benefits are (for) players returning to our team, and a lot of those thoughts and comments are obviously selfish from our side," Salmond said. "We think those players can be a big part in helping us win a gold medal."
Canada hasn't won world junior gold since 2009, when New York Islanders star John Tavares was tournament MVP and Buffalo Sabres centre Cody Hodgson the leading scorer. Last year was the first time Canada didn't medal at the event since 1998.
In the hopes of returning to the glory days of the mid-2000s when winning the gold medal was the norm, Hockey Canada plans on keeping an open dialogue with NHL clubs about players being allowed to go at the last minute.
Rosters do not need to be finalized until Christmas, which leaves plenty of time for things to change.
"We're open with the other teams, let's see what happens in the next three weeks and see where they're at with their decisions with their players, too," Sutter said. "And if doesn't happen, that's fine. We've got a great group of players here, and we'll form a great team out of this group. And if it does happen, that's great, too."
— With files from Lori Ewing.
Follow Stephen Whyno on Twitter at @SWhyno.