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South Side Sox Top Prospect No. 64: Ronaldo Guzman

An aggressive Stateside assignment last season provides a bit of pause on this hot southpaw.

Ronaldo Guzman struggled mightily in 2021 — while pitching against players much older.
Sean Williams/South Side Sox

Ronaldo Guzman

Left-Handed Starting Pitcher
6´0´´
150 pounds
Age: 19
2020 SSHP Top Prospect Ranking: 47
2021 SSS Top Prospect Ranking: 55
SSS rank among all left-handed starting pitchers in the system: 3

Ronaldo Guzman, a native of the Dominican Republic, received a $75,000 signing bonus on Oct. 29, 2018, which may turn out to be the best under-the-radar signing of an international pitcher ever for the White Sox.

In his first taste of professional ball in 2019, he posted a 4.53 ERA and 1.39 WHIP in 14 outings (12 starts) spanning 51 2⁄3 innings. In those innings, he relinquished 43 hits (.221 OBA) and 29 walks (5.1 BB/9) while striking out a whopping 76 (13.2 K/9). While those numbers are outstanding for someone who didn’t turn 17 until late August, Guzman’s numbers would’ve been even better if not for one bad relief outing; throw that bad boy away, and you get an 3.53 ERA and 1.29 WHIP. Keep in mind, also, that Guzman was 2.3 years younger than the DSL average. Certainly his walks were an issue, in addition to a low ground ball rate (37.9%).

Guzman, while striking out his fair share of hitters, struggled badly with his control during his first year Stateside, in 2021 after the 2020 season was lost to pandemic. In 14 games (eight starts) totaling 39 innings this year, Guzman posted an ugly 7.62 ERA and 2.21 WHIP by surrendering 38 hits (.250 OBA) and walking 48 (11.1 BB/9) while fanning 46 (10.6 K/9). Surprisingly, righties hit him less effectively (.228) than lefties (.294). While Guzman did relieve in six games, he fared much better as a starter (6.58 ERA, .245 OBA) WHIP) as opposed to relieving (9.69 ERA, .259 OBA). With any pitcher, it’s vital to get ahead in the count. Guzman, however, took that to an all other level with the ACL Sox:

  • Ahead in the count, hitters hit just .021, giving Guzman a WHIP of 0.07
  • Behind in the count, hitters hit .429 off him, with a 38.25 WHIP.

Ben Badler of Baseball America said this of Guzman prior to the 2019 season: “fastball that gets up to 89 mph with easy arm action and an athletic delivery that repeats well to throw strikes with an advanced changeup for his age.” FanGraphs said this of him after he participated in the 2020 fall instructional league: “he struck out a lot of DSL hitters in 2019 even though he only threw in the mid-80s, because his fastball has big carry. He’s now into the upper-80s and will have an impact fastball if he can keep throwing harder.” Also, because righties hit Guzman less than lefties, it’s safe to assume that he’s got an above-average changeup as well. It’d behoove Guzman to focus on keeping the ball down, as a 29.8% ground ball rate in 2021 was far worse than average.

All is not doom and gloom for Guzman. He still struck out an impressive amount of hitters, and if he can bulk up a bit, his fastball could be expected to gain a few ticks. Also, he was pitching against competition nearly three years older. Before working on forcing hitters to hit more worm-burners, Guzman really needs to focus on improving that control. He has arguably highest ceiling among all the system’s southpaw starters, but he also has one of the lowest floors due to his lack of control and command.

Based on his results this year, expect Guzman to return to the ACL Sox for the 2022 season.


2022 South Side Sox Top 100 White Sox Prospects

64. Ronaldo Guzman, LHSP
65. Laz Rivera, 3B
66. Adam Hackenberg, C
67. Will Kincanon, RHRP
68. Lane Ramsey, RHRP
69. Tommy Sommer, LHSP
70. Randel Mondesi, RF
71. Shawn Goosenberg, 2B
72. Zack Muckenhirn, LHRP
73. Cameron Butler, CF
74. Godwin Bennett, RF
75. Logan Glass, CF
76. Dario Borrero, 1B
77. Craig Dedelow, RF
78. Carlos Hinestroza, RHRP
79. Gunnar Troutwine, C
80. Kade Mechals, RHSP
81: Caberea Weaver, CF
82. Layant Tapia, SS
83. Homer Cruz, RHRP
84. Kaleb Roper, RHSP
85. Jerry Burke, RHSP
86. Emerson Talavera, RHRP
87. Isaiah Carranza, RHSP
88. Davis Martin, RHSP
89. Tyler Osik, 1B
90. Samil Polanco, 3B
91. Manuel Veloz, RHRP
92. Pauly Milto, RHRP
93. Fraser Ellard, LHRP
94. Colby Smelley, C
95. Manuel Guariman, C
96. Everhett Hazelwood, RHRP
97. Garrett Schoenle, LHRP
98. Kyle Kubat, LHRP
99. Anderson Comas, RF
100. Jake Elliott, RHRP