He earned victories at three significant Italian races including the Etna Cup at Catania and the 1100cc class at the 1926 and 1927 Targa Florio where he beat fellow up-and-comer Luigi Fagioli.

Designed with a swept-back aerodynamic front end, a radical innovation uncommon at the time but commonplace today, some felt that Borzacchini had a good chance to capture the prestigious American event.

At the 1932 French Grand Prix and the Coppa Ciano, driving the new Alfa Romeo P3 Borzacchini finished second behind team mate Nuvolari and third at Germany's Großer Preis von Deutschland.

When Alfa Romeo decided to withdraw from racing after the 1932 season and sold its cars to Enzo Ferrari, Borzacchini rejoined the Maserati team, uniting with Luigi Fagioli and Giuseppe Campari.

At the 1933 Targa Florio, held at the Circuito Piccolo delle Madonie, Borzacchini set the pace with the fastest lap before an accident forced him out of the race.

In an effort by the organizers to attract the largest possible crowd, another event called the Monza Grand Prix, using only the banked oval circuit, was staged in the afternoon.

After race officials restarted the event the third tragedy of the day occurred when the car of Polish driver Count Stanislas Czaykowski blew the engine, caught fire and crashed at the same location, burning him to death.