A consistent offensive threat during his stay at Medicine Hat in the Western Hockey League, MacArthur posted two seasons of 30 goals or more and 75, 75 and 74 points, respectively, from 2002-05.

MacArthur also propelled Medicine Hat to the WHL championship and a berth into the 2004 Memorial Cup tournament. Medicine Hat finished 1-2 in the round-robin games, then lost 6-5 to Gatineau in the semifinals. MacArthur, however, was named to the tournament all-star team.

Selected by the Buffalo Sabres in the third round (No. 74) in the 2003 NHL Draft, MacArthur's years in the organization consisted of a series of trips between the parent club and Rochester of the American Hockey League.

MacArthur spent four seasons with the Sabres before being traded to the Atlanta Thrashers on March 3, 2010. He played out the season, became a free agent and signed with the Toronto Maple Leafs on Aug. 28, 2010.

On Nov. 16, 2010, in a 5-4 victory against the Nashville Predators, MacArthur tied a Maple Leafs record by compiling three assists in one period. He would finish the season with 21 goals and 62 points.

Following three seasons in Toronto, MacArthur signed a free agent contract with the Ottawa Senators prior to the 2013-14 season and immediately produced 24 goals and 55 points, which led to five-year contract extension.

Concussion issues would plague his next two years. On Feb. 16, 2015, MacArthur collided with his own goaltender and both players suffered concussions. He was limited to 62 games that season.

MacArthur's 2015-2016 bounce-back season lasted only three games and barely six minutes of a fourth when he suffered another concussion and missed the rest of the season.