Luis Castillo

The 31-year-old was acquired by the Mariners at the 2022 trade deadline and inked a five-year extension two months later; during his first full season with the team in 2023 he posted a 3.34 ERA, 1.10 WHIP and 219:56 K:BB in 197 innings. The campaign ended on a sour note, however, with nine runs allowed in Castillo's final two starts, including a 2.2-frame outing against Texas that eliminated Seattle from playoff contention. His strikeout and walk rates (27.3 percent and 7.0 percent, respectively) stayed stable, but his 1.3 HR/9 was the highest since his sophomore season in 2018. Castillo typically excelled at inducing groundballs while playing for the Reds with a career rate north of 50 percent, but he saw his flyball rate jump nearly nine points to 42.4 percent in 2023 while his groundball rate dipped below 40 percent. A barrel rate of 9.4 percent and hard-hit rate of 41.8 percent each represent career worsts, which also lines up with a 3.81 xFIP. Some regression may be in store for Castillo if he's unable to rein in those trends, but he's still likely a fairly safe bet for fantasy managers in 2024 given his track record.

Castillo was slowed by a sore shoulder in spring training, which in turn made him a great bargain in fantasy drafts. He made his 2022 debut May 9 and really got into a groove in the weeks leading up to the trade deadline, posting a 1.59 ERA, 0.97 WHIP and 41:10 K:BB in what would turn out to be his final five starts for Cincinnati. The Mariners spent a pretty penny in prospect capital to acquire Castillo and the right-hander paid immediate dividends, helping the team to the ALDS. With Castillo, the name of the game is the world-class changeup, set up by a good fastball at 97 mph. The skills only got better after the move to Seattle and the park upgrade is massive. It will be exciting to see what Castillo can do at age 30 in his first full season with a legitimate contender.

Castillo was the worst starting pitcher in the majors through May, posting a 7.22 ERA and 1.78 WHIP over 52 innings. Over the final four months, he was a near ace, posting a 2.73 ERA, 1.20 WHIP and 144 strikeouts in 135.1 innings. Unfortunately, those first two months counted and wreaked havoc, and it's not the first time he has gotten off to a horrific start. It's been suggested by Castillo's agent and others that he's a warm-weather pitcher, and there might be something to that - his velocity was much lower in April and May, especially his peak velocity. There's another big warning sign for Castillo - the diminished effectiveness of his best pitch, his changeup. His K% on that pitch has dropped from 47% in 2019, to 40% in 2020, and all the way down to 28.2% in 2021. When Castillo's draft cost rises in March along with other purported aces, be sure not to get caught up in that inflation.

By FIP, Castillo had a better season than former teammate and NL Cy Young winner Trevor Bauer. The surface numbers lagged way behind his indicators early on, and while they caught up to an extent, Castillo still finished well below where the underlying numbers say he deserved to be. Castillo's changeup is one of the most dominant pitches in baseball, and it plays off a heater that sits 97 mph. His slider has developed into a strong offering, making Castillo something close to a nightmare for right-handed hitters. Great American Ball Park in Cincinnati has not been a problem for Castillo, historically, as he has an ERA nearly a run better at home (3.18) than on the road (4.15 ) in his career. The Reds do not project to be any better with the team cutting costs this offseason, but Castillo is still only 28 years old and this is unquestionably an ace profile on its own merit.

Spring training can be helpful in evaluating a pitcher, but it does come with some risks. Castillo sported a 12.46 ERA over four Cactus League appearances amid reports that his velocity was down. It turned out that Castillo was working on improving his slider, rather than relying more on his two best pitches, his changeup and four-seamer. Given the disparity between Castllo's first half of 2018 when his velocity was down to his second-half when the velocity was up, it was natural to be concerned. That concern cost you a breakout if you downgraded him accordingly. Castillo's fastball velocity (96.5 mph) actually improved, allowing him to post video-game quality results with his changeup (48% whiff rate, .193 WOBA against). If you want to look for a concern, Castillo's August and September were shaky, and he was limited to five starts in September.

Usually it's easy to dismiss first-half/second-half splits, but in the case of Castillo, it's hard to overlook his superb second half, especially when there's an easy explanation for his improvement. Before the All-Star break, Castillo had a 5.49 ERA, 1.65 HR/9, 21.5 K% and 7.9 BB% over 103.1 innings. In 66.1 innings after the break, Castillo turned in a 2.44 ERA, 1.22 HR/9, 26.3 K% and 5.3 BB%. The difference? Every one of Castillo's pitches recovered most of the velocity that he had in 2017 but had lost during the first half of 2018. Take his four-seamer as an example -- in September 2017 it clocked in at 97.3 mph, but in April it was down to 95.4 mph, and stayed down at that level until late July/early August, when it got back up to 96.6 mph (velocity readings courtesy of Baseball Savant). Even with the strong second half, Castillo didn't earn his NFBC ADP of 103.3, but he might exceed that in 2019 if he maintains his second-half velocity.

The Reds had been trying to develop a frontline starter to fill Johnny Cueto's shoes for a couple years, but it came to them in the unlikely form of Castillo, who was involved two trades and one rescinded trade before reaching the majors. He debuted after just 94.1 innings at Double-A and zero experience at Triple-A. Teams didn't figure him out as the year went on -- his ERA actually improved each month from July to September. Castillo was particularly dominant away from Great American Ball Park (2.84 ERA in 44.1 innings). His .247 BABIP, which would have been fifth lowest among qualified starters, will clearly regress. While we can't bank on a repeat of his rookie ratios, he should still be very effective in year two. He throws three pitches -- a fastball that averages 97.5 mph and tops out around 99-100 mph, an out-of-this world changeup and a rapidly improving slider. He has the stuff, command and size (6-foot-2, 190 pounds) to pitch atop a rotation.

Best known for being traded to San Diego and then sheepishly traded back to Miami when Colin Rea's elbow gave out after the trade, Castillo has emerged as one of the best prospects in a desolate Marlins system. He sports an 80-grade fastball with an above-average changeup and two breaking balls that are works in progress, but there is still plenty of time for refinement in the upper levels of the minors. That incomplete repertoire was still more than enough to dominate Florida State League hitters. The lack of strikeouts despite cheddar that touches triple digits illustrates his lack of a consistent out pitch, so he will need to continue to improve those offerings if he hopes to have success as a starter at Double-A and Triple-A. He is relatively new to starting, having worked exclusively as a reliever from 2012 to 2014, so becoming more adept at sequencing will also help him miss more bats. This is an arm that could take a big jump up prospect lists this year, especially now that he's in a Reds' system in the middle of a complete rebuild.