It will be one of at least a handful of pressing questions entering training camp, right up there with how a new system with new assistant coaches is implemented and how an intense battle for forward jobs plays out.

Can the two youngsters step up on the Toronto Maple Leafs blueline and fill what, at this point, appears to be a glaring need?

And, along those lines, can Morgan Rielly not only avoid the sophomore slump but take a step forward after a solid rookie season as a teenager last year?

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Two weeks out from the opening of camp, the focus on Thursday in Toronto was appropriately on the team's back end, as it likely will be for much of the next month.

As Rielly took questions at a news event for video game NHL 15 at the team's practice facility, newcomer Stéphane Robidas made a couple of appearances on local radio stations, dropping the nugget that he isn't yet ready for contact, four months after rebreaking his leg in the postseason.

The other ongoing speculation these days is over whether captain Dion Phaneuf will again be tasked with switching sides – not to play for another team, but to shift to left defence, where he's done duty in the past alongside green partners (Korbinian Holzer, etc.) without much success.

It's the portrait of a D core heavily in flux, with who plays where and who eats the tough minutes anyone's guess.

That's become a talking point for the players, too, specifically Rielly and Cody Franson, the sometimes-partners of a year ago.

"I'm not sure who's going to play with who," Rielly said. "Actually had this conversation last night with Franny about this kind of stuff. We're not sure what's going to happen."

No one is. But if you want to talk "potential problem areas," this is the biggie for a team that gave up a near-record number of shots on goal last season.

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Robidas, while underrated much of his career, is 37 and coming off a devastating injury that can take up to six months to recover from.

Phaneuf had a down year and will, again, be asked to do an awful lot, as his contract dictates. Carl Gunnarsson is gone, leaving a hole on the left side for Rielly or Jake Gardiner to assume top-four minutes permanently, especially given his replacement, Roman Polak, is best suited for No. 6 minutes only.

An injury there, where the Leafs are already thin and counting on prospects to fill in, could be devastating. (Toronto's likely due for this given how few games its defenders have missed the past few years.)

Even if fully healthy, they'll need Robidas to play big, tough minutes.

They'll need Phaneuf to as well – and be better in doing so.

The wild cards there are Rielly and Gardiner, who have become fast friends and roommates, the team's younger "Bert and Ernie" duo in the same vein as Tyler Bozak and Phil Kessel. Unlike those two, their ceiling hasn't been anywhere near established, and their promise was certainly there in what became a mess of a year.

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Gardiner was likely the team's best player as things imploded, logging increasing minutes and piling up 14 points in 21 games in March and April.

Rielly was punted all over the lineup, often playing his off side and splitting his 1,000-plus even-strength minutes almost evenly among four partners – including Tim Gleason and Paul Ranger – as the staff flailed to find an answer on defence.

Put in better situations to succeed, with another year of experience, both could take the next step and handle at least 20 minutes a night. They certainly fit the profile of the direction the Leafs need to go in, relying on speed and puck skills to keep the puck out of their end more often than not.

Their maturation is going to be the Leafs' best-case scenario given what they currently have on the blueline, with holes and question marks aplenty.

Without it, it's hard to see how exactly they've improved.

With it, they've got something to build on.

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"I trained hard this off-season," Rielly explained on Thursday. "I was on the ice a lot [back home in Vancouver] so I feel good. I feel ready. So let's drop the puck already."