Kirby Yates does not have a long track record of success
As mentioned before, Yates was unhittable in 2019 with the Padres. But his other years are not so impressive as you may think. Before joining the Padres, he was a subpar reliever for the Rays, Yankees, and Angels. Although Yates does have a pretty good career 3.54 ERA, that is heavily skewed by his 2019 ERA (1.19).
Credit to Yates for making adjustments and transforming himself into one of the best from 2018-2019, but his numbers from 2014-2017 are a little worrisome. According to FanGraphs, Yates struggled to induce ground balls early in his career. In his 2019 season, he had a 47.9% GB%. In 2014 and 2015, Yates posted a 32.3% and 27.0% GB%.
Yates’ strikeouts per nine innings have trended upwards ever since his MLB debut with the Rays. But again, there are concerns about whether he will have the same stuff after his rehabilitation. In 2019, his K/9 was 14.98. Yates was also able to increase his fastball velocity after joining the Padres, but that remains a big question mark after elbow surgery.
All in all, Yates does have decent career numbers. But if you leave out his 2018 or 2019 season, the numbers tell a very different story. There are many looming questions about how Yates will return in 2021 after rehabbing his elbow. This just adds to the high risk of a player like Yates when you combine it with his 2020 injury-riddled season.