In the 1940s, having settled with his wife Clarice on the Tenuta San Guido on the Tyrrhenian coast, he experimented with several French grape varieties (whose cuttings he had recovered from the estate of the Dukes Salviati in Migliarino) and concluded that the Cabernet had "the bouquet I was looking for."
A wine made mainly from Cabernet Sauvignon was a fundamental change to the Tuscan and Piedmont tradition of Sangiovese and Nebbiolo, respectively. The innovative decision to plant this variety at Tenuta San Guido was partly due to the similarity Mario Incisa had noted between Tuscan terrain and that of Graves in Bordeaux.
The Marchese's first vintages were not warmly received. Critics accustomed to light, local wines were not encouraging; it was not taken into consideration that wines made from the more complex Cabernet Sauvignon grape would need more time to mature and develop. And thus from 1948 to 1967, Sassicaia remained a strictly private affair, only to be consumed at Tenuta San Guido.
Each year, a few cases were stored to age in the Castiglioncello di Bolgheri cellar. The Marchese soon realized that by ageing the wine it improved considerably. Friends and relatives now urged Mario Incisa to experiment further with his project and perfect his revolutionary winemaking style. It was not until 1968 that Sassicaia was first commercially released – the welcome was worthy of a Bordeaux Premier Cru.