He came second in the 1992 German championships behind Jens-Peter Herold thus qualifying for the Olympic 1500 metres competition where he went out before the final. He then got his first international finish with a tenth place at the 1993 World Championships. In a race in 1994 he defeated the Olympic champion Fermín Cacho but finished seventh in the European Championships in Helsinki where Cacho won gold. Later that year, however, Stenzel won the silver medal at the IAAF World Cup behind Noureddine Morceli.