He played college basketball for the Kentucky Wildcats, after being a 5-star prospect in 2016, ranked as high as #14 on ESPN's Top 100.

[3] He played 19:17 minutes in the 2016 Nike Hoop Summit, scoring two points, grabbing four rebounds and dishing out two assists.

He made his debut for the Kentucky Wildcats in an exhibition game on October 31, 2016, against Clarion University, tallying nine points, two rebounds and one assist in 17 minutes coming off the bench.

[6] During his sophomore year, Gabriel became more of a key figure for Kentucky's success that season, tallying 6.8 points and 5.4 rebounds in 37 games.

[12] He had a double-double of 16 points and 16 rebounds for the Stockton Kings on December 20, 2019, in a win over the Delaware Blue Coats.

[14] On January 20, 2020, Gabriel was traded to the Portland Trail Blazers along with Trevor Ariza and Caleb Swanigan in exchange for Kent Bazemore, Anthony Tolliver and two future second round picks.

[29] On October 30, 2023, Gabriel joined the Wisconsin Herd[30] and on March 8, 2024, he signed a 10-day contract with the Memphis Grizzlies.

[34] On July 10, 2024, Gabriel signed a two-year deal with Maccabi Tel Aviv of the Israeli Basketball Premier League and the Euroleague.

[36] On December 23, 2024, Gabriel signed with Panathinaikos of the Greek Basketball League (GBL) and the EuroLeague.

[40] Because his sister – born a year earlier – had died in infancy, Gabriel was given the name "Wenyen", which means "wipe your tears" in his native Dinka language.

[40] Two weeks after he was born, Gabriel's mother, Rebecca Gak, moved with him and his three siblings to Cairo, Egypt to escape the violence of the Second Sudanese Civil War.

[42] He received his paperwork and passport in 2015,[42][43] and represented the USA Basketball Junior National Select Team at the 2016 Nike Hoop Summit.