I mean, in theory if they are interested in any top pitcher (MLBTR predictions/possibilities had them on both Rodon and Verlander) they should be interested in all of them. DeGrom might be the one most likely to take a mega one-year (or opt-out) deal though at his age you'd think he'd want to lock down as much as he could.
Generally speaking I do think it's a logical response to the Harper situation. Upgrade the rotation instead of the line-up; better to have the "problem" of surplus pitching than too many bats.
But yes, without a source that could be anything from a random tweet or sports talk radio guy to an agent leak.