The advanced metrics aren’t predictive because nothing is, but they’re not eye tests.
The 2018 starting pitchers with the lowest xERA — which measures strikeouts, walks, quality of contact and launch angle — were Sale, Verlander, deGrom, Scherzer, Nola, Bauer, Syndergaard, Cole, Snell, Foltynewicz, Flaherty, Kluber, Wheeler, Kershaw, Marquez, Clevinger, Corbin, Morton, Carrasco, Mikolas, Paxton, and Pivetta. Three of those pitchers are younger than Pivetta.
Andriese and Whitlock are swingmen with guaranteed roster spots and Mazza and Springs are decent swingman candidates with options left. I forgot that Brice is out of options, but everyone else in the pen besides Barnes can be sent down.
It seems like there’ll be an especially active shuffle this year to keep everyone’s arms healthy and paced after throwing so few innings in 2020. The 40-man is full before adding Pérez, so I wouldn’t be surprised if there’s a bulky trade in the next couple days.