Just curious.... Let's say the Sox didn't extend Sale when they did, and instead they let him play out 2019, and he put up the same numbers as he actually did.
Now the Sox are left with this decision: Do you sign the newly free-agent Chris Sale (or do you extend him before he hits free agency)? He would have done this in his three seasons with Boston:
2017: 214.1 ip, 17-8, 2.90 era, 157 era+, 0.97 whip, 12.9 k/9
2018: 158.0 ip, 12-4, 2.11 era, 209 era+, 0.86 whip, 13.5 k/9
2019: 147.1 ip, 6-11, 4.40 era, 110 era+, 1.09 whip, 13.3 k/9
Would you even bother signing that guy? Injury issues would definitely be concerning. Also, he would have been on the shelf for all of 2020 due to the TJ he suffered at the end of 2019. So you know you're signing a damaged pitcher, but one who, when healthy, is DOMINANT.
What would a likely contract have been for Sale at that point? No contract at all? SOMEONE would sign him, and probably be willing to take a chance on a decent-sized amount as well. Maybe Boston would still have ended up paying him decent money, even knowing he'd miss all of 2020, but with the assumption (hope? worth the risk?) that he'd be fully healthy in 2021 and back to being CHRIS SALE.
We'll never know of course.