For the moment, act like you are running the Mets and must decide what to do about Jacob deGrom contractually.
You can proceed conservatively. Let him play his two seasons to free agency then decide about trying to keep him beyond 2020. That will cost about $42 million and avoid the exposure of him breaking down in the short term and, thus, wasting money long term.
Conversely, he can stay elite, which would make him enticing throughout the industry, and the cost would be greater than what the Mets might pay now to retain him beyond 2020.