[3] Santini was rated as a top prospect who had been projected as a first round selection of the 2013 NHL Entry Draft.

[9][10] He scored one goal and assisted on 19 as a junior, while helping the BC Eagles to a Frozen Four appearance where they fell short to Quinnipiac.

[14] He scored his first NHL goal on January 12, 2017, against the Edmonton Oilers, due to a puck deflecting off his elbow.

[16] On June 22, 2019, Santini was traded by the Devils along with prospect Jérémy Davies and draft picks to the Nashville Predators in exchange for P. K.

On October 7, 2020, Santini was placed on unconditional waivers by the Predators for the purpose to buyout the remaining year of his contract.

[19] Following three seasons within the Blues organization, Santini left as a free agent and was signed to a one-year, two-way contract with the Los Angeles Kings on July 1, 2023.