Koshigaya Alphas Shake Up Roster: Former NBA Star Sekou Doumbouya Among Five Players Released

The B1 East District landscape shifted significantly on Tuesday, May 12, 2026, as the Koshigaya Alphas announced a sweeping roster overhaul. The club confirmed that five players—including former NBA lottery pick Sekou Doumbouya and Filipino standout Kai Sotto—have reached the end of their contracts for the 2025-26 season and have been officially placed on the free agent list.

The departures mark a pivotal turning point for the Alphas, who are parting ways with a substantial portion of their frontcourt production and international star power. The five players released are Sekou Doumbouya, Kai Sotto, Jordan Nattay, Jarell Martin, and Kayi Sugawara.

The Doumbouya Departure: A High-Production Exit

Of all the departures, the exit of Sekou Doumbouya carries the most weight in terms of sheer statistical impact. The 25-year-old forward from Guinea arrived in Koshigaya with a pedigree that few in the B.League possess, having been selected 15th overall in the 2019 NBA Draft by the Detroit Pistons.

While his NBA tenure saw him appear in 96 games with modest averages of 5.6 points, and 2.8 rebounds per contest, Doumbouya found a different gear in Japan. During the 2025-26 campaign, he evolved into a primary offensive engine for the Alphas. Across 39 games, Doumbouya started 33 times and averaged a dominant 18.8 points, 7.2 rebounds, 2.4 assists, and 1.1 steals per game.

Standing 206cm (6’9″) and weighing 104kg, Doumbouya provided the Alphas with a versatile scoring threat capable of operating as both a small forward and power forward. His ability to create his own shot and defend multiple positions makes him one of the most coveted free agents currently on the market.

Kai Sotto and the Road to Recovery

The release of Kai Sotto is equally significant, not only for the Alphas’ tactical setup but for the massive following he commands in the Philippines. The 24-year-old center, towering at 220cm (7’2″), has had a tumultuous but resilient journey through the B.League.

Sotto first entered the league with the Hiroshima Dragonflies in 2022-23 before a stint with the Yokohama B-Corsairs. However, his tenure in Koshigaya was marred by a devastating ACL tear during the 2024-25 season. The injury sidelined the young big man for a significant period, but he made a determined return to the court in January of this season.

Despite the layoff, Sotto proved his value in 28 appearances, averaging 13.1 points, 9.4 rebounds, and 3.0 assists. His ability to facilitate from the high post and protect the rim remained intact, making his current free-agent status a major talking point for teams seeking a legitimate interior presence.

Roster Vacuum: Nattay, Martin, and Sugawara

While Doumbouya and Sotto capture the headlines, the loss of Jordan Nattay, Jarell Martin, and Kayi Sugawara leaves the Alphas with several holes to fill. The departure of these three players suggests a complete strategic pivot by the front office, moving away from the core that defined their recent identity.

The loss of Jarell Martin is particularly poignant given the team’s recent injury struggles; records indicate Martin had been dealing with a significant injury earlier in the year that sidelined him for over a month in March. By letting these contracts expire, the Alphas are essentially clearing the deck for a new era of recruitment.

The B.League as a Global Hub

This roster churn highlights the evolving nature of the B.League as a premier destination for global talent. The league has increasingly become a landing spot for former NBA first-rounders like Doumbouya and regional icons like Sotto. For these athletes, Japan offers a high level of competition and professional infrastructure, while the teams benefit from the marketing draw and elite skill sets these players bring.

For global fans, the movement of players like Sotto is closely monitored, as his performance in Japan often dictates his standing with the Philippine national team. Any team that secures Sotto’s signature will not only gain a 7-foot center but a massive surge in international visibility.

What’s Next?

The Koshigaya Alphas are now in a race against time to rebuild their core before the next season. With five key players on the free agent list, the club’s front office will likely spend the coming weeks scouting both domestic talent and international imports to replace the lost production.

For the players, the “free agent” label is an opportunity. Doumbouya, now proven as a top-tier scorer in Asia, may look for a return to Europe or a different B.League powerhouse. Sotto, having proven his health after an ACL tear, is now a prime candidate for any team needing a versatile big man.

The next official update from the B.League regarding roster registrations is expected in the coming weeks. We will continue to monitor where these five athletes land.

Do you think the Alphas made a mistake letting Doumbouya walk, or is this a necessary reset? Let us know in the comments below.