During his senior season, Parker scored 25 goals and had eight assists, earning him numerous accolades, including being named the 2010–11 Gatorade New York Boys Soccer Player of the Year.

[15] Vancouver's first opponent in the playoffs was Portland, and despite Parker playing every minute of both legs, the Whitecaps would lose 2–0 on aggregate to the eventual MLS Cup champion Timbers.

[12] The first match of the 2017 season for the Whitecaps came on February 22 in the Champions League knockout stage, a 1–1 draw with the New York Red Bulls in leg 1 of the quarterfinals.

[19][20] Parker ended the regular season with 32 appearances, one goal and one assist, helping the Whitecaps finish 3rd in the Western Conference and qualify for the playoffs.

To sign a guy like that is unbelievable for us.” On March 2, 2018, Parker was traded to the New York Red Bulls in exchange for Felipe, $500,000 in targeted allocation money (TAM), and a 2018 international roster slot.

[23] On March 6, 2018, he made his Red Bulls debut, appearing as a starter in a 2–0 victory in Mexico over Club Tijuana in the CONCACAF Champions League.

Parker made four appearances in the Champions League as New York reached the quarterfinals, where they lost to Santos Laguna with an aggregate score of 6–2.

[12] He made 31 MLS regular season appearances in 2019, helping the Red Bulls finish 6th in the Eastern Conference and qualify for the playoffs.

[14] On October 20, scored in the Red Bulls opening game of the playoffs, however, New York would lose 4–3 to the Philadelphia Union in extra time.

[30] On October 28, 2020, Parker got an assist in the 89th minute to give the Red Bulls a 1–0 win over the New England Revolution, heading a corner kick onto Aaron long, who put the ball into the net.

[14][32] In the Red Bulls' first playoff game, Parker played the full 90 minutes, but New York lost to eventual MLS Cup champions Columbus Crew 3–2.

[35] Parker played every minute of the season for Houston, making 34 appearances, however the team did not enjoy a successful campaign, finishing last in the Western Conference and failing to qualify for the playoffs.

[38] On November 11, 2022, Parker was traded to St. Louis City SC ahead of their inaugural season for $500,000 of GAM, with Houston paying a portion of his salary.

[41] On August 2, 2024, St. Louis City traded Parker plus $600,000 in General Allocation Money to the New England Revolution, in exchange for Henry Kessler.