For whatever reason, Best Supporting Actor is, year after year, the easiest acting race to predict. It is often narrowed in on one or two candidates long before the Screen Actors Guild announce their awards. The SAGs just act to solidify the already established front-runner.
2019, by and large, shows the same conditions. The race is already narrowed down, and it is not hard to pick a winner before the SAGs even happen. There is always upset potential, but this race is much more predictable than the other categories.