Luis Castillo was T-24th last year in fWAR for SP with at least 100 IP. I dropped it down to get guys like Strider, Kershaw, and Snell included in my results. He had a mark of 3.7 on the season in 150 innings.
Honestly, after watching the way he pitched after getting to Seattle, I think we see a better pitcher than that. You have a guy leading the way on a potentially great team, who showed that he can dominate when it matters. We still might see the odd hiccups against a team like Oakland, but he did have a better FIP in Seattle as opposed to Cincinnati.
Here's what STEAMER projects for Luis Castillo.
3.34 ERA, 3.40 FIP, 3.5 fWAR, 195 IP, 9.5 K/9, 2.9 BB/9, .293 BABIP, 12-10 record
The fact that they are predicting 195 IP, but only a 3.5 fWAR stands out to me. Even with a lower fWAR per start after coming to Seattle last year, that would still put him on pace for 4.5 fWAR based on last years numbers with the Mariners. If you are telling me that you are getting 6 IP per start from Castillo, I'm guessing that he is feeling it and dealing. Especially if you're calling for 206 Ks.
The 12-10 record seems odd as well. That seems to be a lot of losses to hand out to him. I can't argue too much with STEAMER when they are prognosticating off of the last three years, but I feel good that he is going to do a bit better than what they predict.
2.91 ERA, 3.27 FIP, 5.2 fWAR, 197 IP, 10.4 K/9, 2.4 BB/9, .285 BABIP, 16-7 record
If we truly believe that the Mariners are going to be a good team with a grasp on a playoff spot, this seems like a line that is more likely to happen. The Ks go up to 227, the wins go up with the Mariners fighting for 94-98 wins on the season, and he has a lower BABIP with a solid defense behind him. Sure, it's optimistic, but I don't think it's crazy when you look at what he did vs TOR and HOU.
However, if those STEAMER projections are what we end up seeing for Luis Castillo, then things aren't all that bad. He would still be a solid guy amidst the top of the rotation, but fans would likely be a bit underwhelmed by the numbers after he signed the new contract. Let's hope that 2023 Castillo is closer to what I listed instead of what STEAMER does. Who doesn't want to root for Castillo as a dark horse CY Young candidate?