[2] Ustorf came through the youth ranks of ESV Kaufbeuren and made his debut in the German top-tier during the 1991–92 season.

[3] After a few years in the minors, with stints in the AHL and IHL, he returned to play hockey in Germany.

Ustorf played for DEL teams Adler Mannheim, Krefeld Pinguine and then spent eight years with Eisbären Berlin, winning six German championships.

Whilst still suffering from post-concussion symptoms 14 months later, and other non-related injuries, Ustorf announced his retirement at the tail end of the 2012–13 season on March 7, 2013.

[6] On May 10, 2014, Ustorf was named director of sport at Eisbären Berlin[7] and moved to the role of head of player development in May 2017.