Fair question LongD, when does Burk's price go up? IMHO, if he stays healthy and the last couple of games will be his 2017 norm, length, guaranteed and probably a bit per year average bump. He's making (???) somewhere in the ballpark of 3.5 million this year with the Patriots on a one year deal. So unless he is a feature back, 3.5 avg isn't far off from what I'd expect the per year average offers to be.
Rex is in the driver seat if he keeps playing like this. He either says "I like it here" and he negotiates an extension/signs when possible, gets the 6(?) million signing bonus and becomes a longer term Patriot. Or he says "I want to make as much money in 2018 as possible" and hits FA to maximize offers. He is likely to get a better offer than the Patriots and maybe that's what he wants. He did sign that 1 year deal which suggests that was his plan all along.
Again if the last 2 games is the Rex for rest of 2017 then he's got good choices coming up. I just am dubious when it's only a couple games sample especially when one game is against a Denver team that appears to have the inability to play pass D against non WRs. But then again I am eternally skeptical of everything