And in doing do you will have changed the following contract:
2019 (27): $5.5M guaranteed
2020 (28): ~$9M option, $0 buyout
2021 (29): ~$13M option, $0 buyout
into:
2019 (27): $5.5M guaranteed
2020 (28): ~$9M guaranteed
2021 (29): ~$13M guaranteed
2022 (30): ~$15M guaranteed
The Braves will have taken on 3 more years of guaranteed seasons, 2 of which they already control with cheap options that could be declined at any point, in exchange for 1 season of a 3+ win pitcher who is likely entering his decline phase.
The risk/reward doesn't seem justified. Age 30+ seasons for SPs simply aren't valuable enough to justify guaranteeing the arb years.
I'll do a simplified scenario analysis that gives an idea of why the risk may be worth taking.
Lets say there is a 20% chance of some catastrophic injury. And to make the whole thing easier to analyze, let's say the injury happens right at the end of 2020. Let's further assume he is a 3 WAR player if that catastrophic injury doesn't happen (not terribly realistic but makes the analysis easy).
Now lets look at two scenarios. Scenario 1 is the team takes him to arb year by year. Scenario 2 involves signing him for 1 free agent year with an option for the second year at the market price for a 1.5 WAR player.
Since the injury happens at the end of 2020 we need to consider what happens after 2020 in the two scenarios.
Scenario 1
80% chance no injury: 3 WAR season in 2021. 1.5 WAR of surplus.
20% chance of catastrophic injury at the end of 2020. Team releases him with no loss to the club.
Expected surplus is .80*1.5 or 1.2 WAR
Scenario 2
If no injury you get 3 WAR seasons from him in 2021, 2022 and 2023 with a surplus of 1.5 each year. Total surplus 4.5 if no injury.
If injury you are on the hook and pay 1.5 WAR for no production in 2021 and 2022.
Expected surplus is .8*4.5-.2*3=3.6-0.6 or 3.0 WAR
To make this whole thing easy to analyze I did make some simplifying assumptions. You may want to try other assumptions (for example 10% injury risk at the end of each season). You can also do an aging curve so that in the absence of catastrophic injury he is a 3.2 WAR pitcher in 2021, 3.0 in 2022 and 2.8 in 2023.
The catastrophic injury could happen the day after he signs the contract. I concede in that scenario the contract is a bad deal.