Cassini started his own career under Bo Kristofferson, who at that time was the chief trainer at the Holstein Verband and in the meanwhile is now the national trainer for the Danish team. In 1999, Cassini and Franke Sloothaak were members of the winning German team for the Nation Prize in Modena, Italy and that same year they were just barely beaten in the Puissance at Mauberge, France, finishing second. They had also won the Grand Prix in Arnheim in 1998. This gray entered the World Cup Tour twice before retiring from sport in 1999, after which he was used exclusively for breeding. "Cassini had unbelievable potential and his jumping technique, which was absolutely exceptional, was envied by many."

 

Cassini I stands to a full book of mares each year. Cassini has over 2 thousand requests per season for mares to fill his book. He is currently the sire to over 30 approved sons world wide.