Rielly has earned enough respect in this league, and with the cap jumping like crazy, that there would be a lineup of teams more than happy to trade for him even with 5 years at $7.5m remaining. He is the 27th highest paid defenceman in the league this year.
As for production, much is made of the fact that the Leafs don't get much production from their blueline, but I think that has more to do with how the Leafs are attacking the game than him all of a sudden forgetting how to play hockey.
It's also worthwhile noting that he hasn't exactly had the best stable of partners this year.. His even strengh partners have been OEL (38.3% of the time), Myers (24.8% of the time), Tanev (14.7% of the time), and Timmins (8.2%) of the time. He's not an ideal fit OEL, and Myers/Timmins are #7-quality defencemen in the NHL.
Also interesting to note, that his on ice-shots percentage when playing with Tanev was 58.4% and Corsi 53.8%.... which is actually better than the Tanev-McCabe pairing.
I know +/- is a flawed stat... but I think it's also worth noting that McCabe-Tanev are a +8 (51% of Tanev's EV-TOI) together, while OEL-Tanev are a +8 in 21% of Tanev's time (less than half).
I think there's a really strong case to be made that the left side of the Leafs D needs to be Rielly, McCabe, and OEL; with an understanding that a right side of Tanev, Myers and Timmins is obviously not good enough.