Klingberg has been pacing around 50 points the last 4 years (5 years ago was the last time he even paced above 60 points). Rielly has had a 68 and 72 point season in that time, has been pacing almost 65 points overall the past 4 years, and Rielly has relied less on PP to put up those points. Rielly has a been better defensively as well, and he has had less support than Klingberg in terms of his partners.
Now obviously our offense is better than Dallas', so it is probably easier for Rielly to put up more points. But we are talking about 10-15 more points, and he is a better overall defenseman than Klingberg (at least since Klingberg was like 25).
I think teams are looking at Klingberg as an offensive defenseman who has not really put up elite production recently and they are not willing to commit to the term at this point. One year at 7 mill is actually more than I thought he would get, so he did fairly well there. It is a lot like Hall and I imagine if he doesn't totally suck, he will get something in 5.5-6.5 mill range on a 4 or 5 year deal next offseason. It is not a bad bet for him because at least he is getting more than he is worth for that one year and he is going somewhere where he can really showcase himself before moving to another team at the TDL.
The main thing I think more than anything is he needs another playoff like the 21 points in 26 games when Dallas went on their Cup run, and not the 1 point in 7 games like this past playoffs.