We have not heard any rumors about Rielly this summer, but the same cannot be said for Mitch Marner. Many Leafs fans are expecting the team to finally switch up the core-four after they lost yet again in the first round of the playoffs. Considering that Nylander and Matthews just signed extensions, that leaves Tavares and Marner as the tradable options. Tavares however, is showing signs of age-related decline and thus has diminishing trade value. As a result, Marner has seemed to be the odd man out.
However, that does not factor in the Leafs defense. Sure, Morgan Rielly is not technically a core-four guy, but moving him would still open up 7.5 million dollars in cap space. While Marner has a full no-move clause, Rielly only has a 10-team no-trade list, which he submits at the beginning of each season. Thus, moving Rielly would not only keep the core-four together, but it would also be easier.
Of course, moving Rielly would mean the Leafs would have to dedicate a lot of resources to filling out their blueline. They would need a new number one defenseman in addition to more depth on the backend in general. That doesn't mean it can't be done though. Be sure to stay tuned to see what the team does.