The US team member claimed first, third, fourth and fifth places in the $5,000 Horseware Ireland Welcome Stake at TIEC.
The German edged Swedish rider Peder Fredricson who has been riding the Olympic momentum, placing second aboard H&M Christian K.
Fresh off his Olympic gold and silver medals, the Swedish rider narrowly beat British superstar John Whitaker for top spot.
Highlights from the Summer Series include Sybil Moylan (daughter of Canadian rider Gavin) and Churchill being named Leadline champions.
The final grand prix of the Ocala NSBA Summer Series saw a win for the US rider; Canadian Angela Covert was 9th riding Hollywood De Rase Z.
The American rider has enjoyed great success at World Equestrian Center-Ocala, and this marked his eighth Grand Prix victory.
The top 30 tackled Santiago Valera’s large and demanding course with Deslauriers picking up 13 penalties during his trip.
Deslauriers and the Holsteiner mare sailed around Santiago Valera's colourful Olympic course clear in the 5th-best time of the day.
The Jumping Individual Qualifier will take place on August 3, with the top 30 combinations moving on to the Individual Final.
The FEI Jumping European Championships Young Riders, Juniors, Children 2021 has wrapped up in Vilamoura, Portugal.