Before moving to Austria, Otten established a distinguished reputation in the Netherlands, most notably as the Head Coach of Donar Groningen. During his tenure there, he achieved significant milestones, including clinching the Dutch Cup championship, securing a spot in the BNXT League Finals, and guiding the squad through two competitive seasons in the FIBA Europe Cup. His arrival at Donar was preceded by a highly impactful period at rival club Yoast United, where his strategic leadership propelled the team to a breakthrough appearance in the 2021 Dutch Cup finals. Beyond his club responsibilities, Otten has been a prominent figure in international basketball; he served as an assistant coach under Maurizio Buscaglia, playing a vital role in helping the Dutch senior national team qualify for EuroBasket 2022, while simultaneously spearheading the development of young talent as the Head Coach of the Netherlands U18 Men's National Team. His coaching journey began immediately following his retirement as a professional player, when he transitioned into the role of assistant coach for the SPM Shooters, working closely under the mentorship of head coach Sam Jones.