Growing up he was a member of Congregation Shir Shalom, and he wears a Star of David necklace while pitching.

[6] In his senior year, as a pitcher he had an 8–1 win–loss record with a 1.52 earned run average (ERA), and struck out 60 batters while allowing 14 walks in 55 innings pitched.

[16][17] The Jewish Sports Review named Effross to their 2015 Division I College Baseball All-America team.

[18][19] He finished his college career with 81 pitching appearances (fourth all-time at Indiana University), tied for fifth with 12 saves, and was seventh with a 2.27 ERA.

[21] Effross was 5–2 with nine saves (4th in the Carolina League) and a 3.40 ERA in 42 games (3rd), including 2 starts, covering 79.1 innings in which he gave up only one home run.

[21] In 2021, Effross split the season between the Smokies, now in the Double-A South, and the Iowa Cubs of the Triple-A East.

[28][29] He was at the time in the top 5% of major league pitchers in keeping batters to a low barrel percentage, and inducing a high chase rate.

[29] With the Yankees in 2022 he was 0–0 with 3 saves, 3 holds, and a 2.14 ERA in 13 relief appearances in which he pitched 12+2⁄3 innings, with a 1.026 WHIP, in high-leverage situations.

[35] He threw mostly an 80-mile-per-hour (130 km/h) sweeping slider (against which batters hit .149) and 90-mile-per-hour (140 km/h) biting sinker, with a less frequent 83-mile-per-hour (134 km/h) changeup and 91-mile-per-hour (146 km/h) heavy sinking 4-seam fastball.

He also missed the entire 2023 season; rehabilitation and recovery from Tommy John surgery generally take at least 12 months, and often longer.

[33][39] On February 14, 2024, it was announced that Effross would miss multiple months as a result of a December low back surgery, and he was subsequently placed on the 60–day injured list.