- Bats Left, Throws Right
- Height 6' 7", Weight 210 lb.
He was originally signed as an international free agent by the Los Angeles Dodgers on July 2, 2015 and began his pro career the next season with the DSL Dodgers 1 where he hit .294 in 55 games. In 2017, he moved stateside with the Great Lakes Loons of the Midwest League and as an 18-year-old in full-season ball hit .240 in 89 games. On July 31st, he was one of two minor leaguers traded to the Pirates for reliever Tony Watson, the other being reliever Angel German, and he finished the season in the South Atlantic League, with the West Virginia Power, where he hit .218 in 16 games. In 2018, he had a break-out season for West Virginia, hitting .286/.343/.488 in 103 games, with 25 doubles, 7 triples and 14 homers. he was a post-season All-Star and named the league's Most Outstanding Major League Prospect after the season.
In 2019, Cruz played at three different levels, including a short rehabilitation assignment with the GCL Pirates after fracturing his right foot at the end of April. He hit .301 in 35 games for the Bradenton Marauders, then as assigned to the AA Altoona Curve at the end of July where he played another 35 games, hitting .269. Altogether, in 73 games, his batting line was ..298/.356/.475 with 8 homers and 34 RBIs. He was named a Pirates organizational All-Star by MiLB.com, after having been the Florida State League Player of the Month in July. The future looked very bright, and in 2020, he was one of the minor league prospects added to the Pirates' 60-player pool, spending the year at their alternate training site in Altoona. When the camp was wound down in early September, he returned to his native Dominican Republic and in the early hours of September 21st, was involved in a tragic vehicular accident when he was driving his Jeep on a highway near the town of Bani, Peravia, and hit a motorcycle carrying three persons, killing all three. The motorcycle was traveling without lights, while Cruz, who was not injured, was suspected to have been under the influence. Both vehicles were breaking a curfew imposed by authorities because of the Coronavirus pandemic. Cruz was arrested at the scene and faced significant prison time if convicted of impaired driving, but he was cleared of charges. He vehemently denied having been under the influence, and it was confirmed that he was the one who had called for emergency assistance after the accident. He also had an explanation for why he was breaking curfew, which was that he was taking his ailing child to a hospital, while his wife, who was pregnant at the time, was home sick. In the end he was not charged with any offense, as the crash was determined to be a tragic accident, and he was able to play in winter ball.
He made his major league debut in the penultimate game of the 2021 season, on October 2nd, two days before his 23rd birthday. Against the Cincinnati Reds, he started at shortstop and batted 8th, going 2 for 5 with a run scored and 2 RBI in an 8-6 win. He then hit his first career homer in his only other game, finishing 3 for 9. He was the tallest man to start at shortstop in major league history. Before his late promotion, he had finished the minor league season on fire, belting a homer in five of his 6 games for the AAA Indianapolis Indians; he had previously played 62 games in AA with the Altoona Curve, after missing time with an elbow injury, finishing a combined .310/.375/.594 between the two stops, with 16 doubles, 5 homers and 17 RBIs.
At 6' 7", Cruz is much taller than the average shortstop - in fact there have hardly been any over 6' 4" in professional baseball history, but that was the position he played for most of his first four minor league seasons, because of his outstanding athleticism. He was viewed as a likely third baseman or outfielder in the longer term. He is named after Paul O'Neill, who was his father's favorite player. His father, Rafael Cruz, played three seasons in the minors, and his brother Homer Cruz has also played in the minors.
- Chris Bumbaca: "Pirates prospect Oneil Cruz under influence of alcohol in crash that killed three in Dominican Republic, per reports", USA Today, September 23, 2020. 
- Jake Crouse: "Bucs prospect Cruz called up for MLB debut: 6-foot-7 shortstop becomes tallest to start at spot in AL/NL history", mlb.com, October 3, 2021. 
- Jason Mackey: "Authorities: Pirates prospect Oneil Cruz had alcohol in system at time of fatal crash", Pittsburgh Post-Gazette, September 22, 2020.