Despite being retired in the summer of his second season, Mariacci defeated many of the best French horses of his era including Allez France, Ivanjica, Green Dancer, Val de l'Orne and Nobiliary.
Mariacci began his racing career in the Prix de Crèvecœur for previously unraced horses over 1400 metres at Deauville Racecourse in August and won by three quarters of a length.
Rivases employed exaggerated waiting tactics, delaying his challenge until the last 200 metres but Mariacci maintained his unbeaten record, winning by a nose and a head from Good Point and Top Gear.
Green Dancer was sent to England for The Derby and in the Prix du Jockey Club over 2400 metres at Chantilly Racecourse on 8 June Mariacci started second favourite behind Val de l'Orne.
After fighting Rivases's attempts to restrain him in the early stages he looked likely to make a serious challenge in the straight before finishing third, beaten a head and two and a half lengths by Val de l'Orne and Patch.
[2] There was no International Classification of European two-year-olds in 1974: the official handicappers of Britain, Ireland and France compiled separate rankings for horses which competed in those countries.
In the official French handicap he was rated the fourth-best three-year-old colt of the year behind Val de l'Orne, Patch and Green Dancer.