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Colorado Rockies prospects: No. 21, Antonio Santos

The 24-year-old right hander has promise, despite a rather disappointing major league debut in 2020

21. Antonio Santos (112 points, 11 ballots)

Antonio Santos represents a late bloomer for the Latin America program, which unfortunately has had a fallow few years for the Rockies until recently. The 24-year-old right-handed Dominican starter was only signed when he was 18 (in 2015) for a $50,000 bonus. Over the last six seasons, he’s slowly worked his way up the minor league ladder to get a big league cameo in 2020.

In his first four professional seasons, Santos distinguished himself with his ability to soak up innings (he threw over 140 each year from 2017-2019) with good K/BB numbers against older hitters (as perennially one of the youngest players in each league he played in). In 2019, Santos began the year as a repeater in High-A Lancaster against hitters that were on average about 1.2 years older in one of the most intimidating environments for pitchers in all of minor league baseball. On this canvas, the 4.35 ERA, 3.74 xFIP, 1.35 WHIP, 8.7 K/9 rate, and 1.6 BB/9 rate Santos put up in 99 1⁄3 innings over 18 starts is a strong performance.

The Rockies agreed, moving him up to Double-A Hartford in late July. In a more neutral environment but against hitters that were on average about 2.3 years older, Santos fared well. In eight starts with Hartford, Santos threw 45 2⁄3 frames of 4.93 ERA, 3.21 xFIP, 1.25 WHIP, 8.7 K/9, 2.0 BB/9 ball. That performance was enough to get Santos on the Arizona Fall League roster where he appeared as a reliever in eight games, throwing 13 innings with a 16:2 K/BB ratio and 2.77 ERA against fellow top prospects. The showing secured Santos as a prospect worth a 40-man roster slot.

In 2020, Santos mostly stayed at the alternate site, but did get the call to The Show in late August. He made his debut on September 1st in long relief with 2 13 innings, allowing two runs on four hits in what would become a 23-5 loss. Santos didn’t get into a game for another week, when he was again called in for long relief duty in a blowout loss: this time three innings, three runs, five hits in a 14-5 loss. Santos was sent down for ten days, but didn’t get in a game for another six days after being recalled. This time, Santos was the starter, but he got knocked around hard — lasting only one out and allowing six runs on five hits in a game the Rockies would lose 11-5. And that was it for Santos in a disappointing 2020: three appearances, six innings, 11 runs on 14 hits and a ghastly 16.50 ERA (-0.3 rWAR).

Here’s some video of Santos from the AFL courtesy of 2080 Baseball, where his fastball sat in the mid-90s:

Accompanying the above video is this report from 2080 Baseball’s Adam McInturff, complete with granular arsenal and mechanics grades (overall a 45 FV grade as a set-up reliever). The whole thing is worth reading, but this is the summary:

Big stuff without pitchability/consistency to fully harness it in SP role; strikethrowing over 3-4 power pitches and ability to pitch multi-inning stints give high-end 7th inning or decent setup RP upside; like him in the ‘pen and could come quickly there.

Santos was ranked 19th in the system before the 2020 season by Jeffrey Paternostro of Baseball Prospectus:

Santos is an interesting arm strength flyer. He can run his fastball up into the upper 90s—and sit mid-90s in short bursts—but the pitch tends to run a little true, and a violent finish to his delivery suggests the command profile may not be fine enough to start. He does have a little hitch/hesitation which can create timing issues for the hitters, and he’s effectively wild with the heater.

Santos has a full four-pitch mix, but both breaking balls are below-average—a slurvy curveball will occasionally flash decent tilt—and the changeup is inconsistent. The change will at least flash some hard fade and dive, but it’s firm, and fastball/changeup relievers are a rare bird. There’s some swing/spot start potential here and maybe you can get one of the breakers to average to give him a shot at middle relief, but it’s a tough major league profile even before you consider his future home park.

The pre-2020 FanGraphs evaluation gives him a 40 FV, ranking him 22nd in the org:

Santos’ fastball velocity range is rather vast, but when he was coming out of the bullpen during Fall League, he was sitting 94-97 for entire outings. He doesn’t have a bat-missing secondary; rather he has a deep well of average pitches from which to draw. Whether he’s a No. 5/6 starter type or his repertoire gets pared down to what Colorado thinks gives him the best chance of missing bats out of the bullpen, we think Santos is clearly a rosterable arm of some kind. ranks Santos 27th in the system:

Santos has perhaps the best control in the system, with a walk rate of 1.7 per nine innings over the course of his career, and has the chance to have a decent three-pitch mix to go along with it. In shorter stints in the AFL, his fastball velocity crept up and he was 94-96 mph and was sitting 95 mph. His secondary stuff, a slider and changeup, aren’t as good as his fastball, but could be average pitches in time. He’ll need them to take a step forward so he can have something resembling an out pitch to complement his firm fastball.

Thanks to a simple delivery and arm stroke, Santos consistently fills up the strike zone, though the lack of premium stuff has caused him to be hit at times. If he can refine his secondary pitches, he could be a No. 5 type starter, but the Rockies now know his repertoire ticks up a bit in shorter stints out of the ‘pen.

The consensus on Santos does appear to be that his future is in middle/long relief, though his track record indicates the durability of a starter if he can improve his secondary offerings. 2020 obviously wasn’t a good outcome for Santos, but a) it was a small sample size and b) Santos clearly was out of his rhythm for at least the first two outings. I can see him competing for a bullpen slot or even the fifth rotation spot in Spring Training this year, and it’s quite likely he’ll at least fill in at one of those slots sometime during the 2021 season.

It’s not hard to see a MLB outcome for Santos that mirrors that of past Rockies Latin America starter prospects with blah secondary pitches like Juan Nicasio and Antonio Senzatela — a back-end starter better suited to middle relief or set-up work at the big league level. Then again, Senzatela showed that profile could be quite successful in 2020. That said, every prospect is different and I don’t want to put Santos in that box just yet. He is still very much an interesting starter candidate worthy of a 40 FV grade and a ranking of 19 on my personal list.