Cijntje was born in the
Netherlands and grew up primarily in
Willemstad, Curaçao. He
switch pitched and played shortstop for Willemstad in the
2016 Little League World Series. Cijntje played second base and batted second for
the Netherlands under-15 team at the
2018 U-15 Baseball World Cup in Panama. He had a 1.076
on-base plus slugging and 6 RBI while committing two
errors in eight games at the tournament. He also participated in the
Reviving Baseball in Inner Cities (RBI) program in Curaçao. Cijntje moved to
Miami when he was 16 years old, where he lived with three older cousins who had played
college baseball at
Florida National University. He attended
Champagnat Catholic School in
Hialeah, Florida, where he played baseball as both a switch pitcher and
switch hitter. His high school
record was 7–6 with a 2.32
earned run average (ERA), striking out 166 batters in 81 innings. He committed to play for
Mississippi State University before his senior season. He enrolled there after not signing with the
Milwaukee Brewers, who selected him in the 18th round of the
2022 MLB draft as a shortstop. Because he threw right handed as an infielder, his right throwing arm became stronger than his left. In his first collegiate start, he struck out seven
Louisiana–Monroe batters, six while pitching right-handed and one as a lefty, while allowing one hit and one walk over four innings. He finished the season with a 3–5 record and 8.10 ERA in 14 games, 13 of the starts. He had 63
strikeouts in 50 innings pitched. As a sophomore in 2024, Cijntje was named a second-team
All American by the
National Collegiate Baseball Writers Association and Perfect Game and was named to the South All-Region first team by the
American Baseball Coaches Association. He finished the season with an 8–2 record and 3.67 ERA over 16 starts. He had 113 strikeouts in innings pitched. Mississippi State pitching coach Justin Parker said Cijntje would often forego the
platoon advantage and pitch with his right arm to left-handed batters to improve his consistency. Parker said Cijntje had higher velocity and better command with his right arm but induced more groundballs as a lefty. ==Professional career==