A lot of things went right for Hyun-Jin Ryu in 2019, many of which were likely to regress to the mean in 2020 even before he chose his new team.
By signing with the Toronto Blue Jays, for a reported four years and $80 million, he further increased said regression prospects -- even if only by a little.
Injuries have been a constant problem for Ryu in his seven years in the U.S., as he's one of only five players to have made as many as 10 trips to the injured list during that time span (Aaron Hicks 12, CC Sabathia 12, Francisco Cervelli 11, Martin Prado 10). His 21 days missed in 2019 were his fewest since his completely healthy U.S. debut season of 2013. Those who took the chance on him last season were handsomely rewarded, but can he repeat such a healthy year?
There's no fixed answer to that, but in between his ailments, Ryu has ranked among the best at his craft. From 2013-19, and among the 232 pitchers who made at least 50 starts in that time, his 2.98 ERA ranked sixth-best, his 1.16 WHIP 29th-best and his 4.05 strikeout-to-walk ratio 25th-best. Last season alone, he was the No. 24 overall name and No. 9 starting pitcher on the Player Rater, thanks to a major league-leading 2.32 ERA, sixth-ranked 1.01 WHIP and 14 wins in 29 starts.
In Toronto, Ryu will have to deal with American League competition for the first time, which always elicits a negative reaction from prospective fantasy managers of league-switchers due to the presence of the designated hitter. It's a correct impression, but it's also not as severe as you might think: AL teams averaged 4.88 runs per game in 2019, compared to 4.78 for National League squads. That difference is due almost entirely to DHs' (both leagues) .247/.328/.455 slash rates in 10,458 trips to the plate, compared to pitchers' .128/.159/.163 in 5,098 last season.
The ballpark switch is another small negative for Ryu, considering Toronto's Rogers Centre was the game's most home run-friendly environment in 2019. But during the five seasons that preceded it -- a wiser sample with which to judge -- Rogers Centre ranked only one spot higher on that list (1.067 factor, 10th in the majors) than Los Angeles' Dodger Stadium (1.061, 11th), with the primary difference between the two venues being run scoring, where Rogers Centre was slightly better than neutral (1.031, 10th) and Dodger Stadium leaned clearly pitching-friendly (0.952, 21st).
The Blue Jays nevertheless landed themselves a true ace, at least during the times Ryu is available to the team. He seemed to fade late last season, perhaps from his having stayed remarkably healthy, In 11 second-half starts, he had a 3.51 ERA and 1.16 WHIP, slipping from his first-half status as the NL's clear Cy Young favorite.
Perhaps another relatively injury-free campaign would allow Ryu to extend his success through the entirety of the seasonal schedule, but I'd bank on his 2020 ERA rising to 3.00 and probably slightly higher. He's not a pitcher I'd draft any sooner than 25th at his position, and in fact I think he's only a 50/50 shot for the top 30 -- not that that's a damning evaluation of his year to only barely reach that group.