[7] In his sophomore season with the Eagles in 2015–16, Sanford continued his offensive output and recorded 39 points in 40 games as the team qualified for the Frozen Four.

[3] On July 11, 2016, Sanford embarked on his professional career in signing a three-year, entry-level contract with the Washington Capitals.

[10] He made his NHL debut on October 13, 2016, against the defending Stanley Cup Champion Pittsburgh Penguins and had one shot on goal.

After being sent down to American Hockey League (AHL) affiliate, the Hershey Bears, he was recalled up to the NHL on February 10.

Sanford added another goal and assist in 26 games with the Capitals before he was traded to the St. Louis Blues as part of a package for defenseman Kevin Shattenkirk on February 27, 2017.

[15] He was activated from the injured list on February 15, 2018 and re-assigned to the Blues AHL affiliate, the San Antonio Rampage.

[22] The changes proved to be successful as Sanford ended the regular season playing in 60 regular-season games and accumulating 20 points and the team qualified for the 2019 Stanley Cup playoffs.

[27] It was also Sanford's first career hat trick and the first time a Blues' player scored four goals in a game in over five years.

[32] On September 25, 2021, Sanford was traded to the Ottawa Senators for forward Logan Brown and a conditional fourth round pick.

[43] Sanford was recalled by Arizona on October 23 after injuries to Coyotes' forwards Jason Zucker and Michael Carcone.

[44] Sanford made his season debut for the Coyotes on October 27 versus the Los Angeles Kings, registering an assist.

[47] He made his Blackhawks debut in a 4–3 victory over the Calgary Flames on January 7, registering his first point with the team when he assisted on Colin Blackwell's game winning goal in the third period.

[49] On March 15, he was assigned to Chicago's AHL affiliate, the Rockford IceHogs, to make room for forward Lukas Reichel.