Donovan made his University of Denver debut on October 9, 2009, and completed his first season as a Pioneer with seven goals and 14 assists for a total of 21 points in 36 games to lead all Western Collegiate Hockey Association (WCHA) defenseman in goals.[2] For his efforts he was rewarded by being named to the Inside College Hockey Freshman All-American team, All-College Hockey News Rookie Team, and All-WCHA Rookie Team.[3]
Donovan made his NHL debut on April 3, 2012, against the New Jersey Devils, making him the first Oklahoman born, raised, and trained in the state to play in the NHL. Donovan wore uniform number 46 in honor of Oklahoma being the 46th state.[6] After making the Islanders' roster to start the 2013–14 season,[1] he scored his first NHL goal on October 8, 2013, against Mike Smith of the Phoenix Coyotes.[7]
With the Islanders declining to give Donovan a qualifying offer, on July 1, 2015, the Buffalo Sabres signed Donovan as a free agent to a one-year contract.[8]
Donovan enjoyed two productive seasons in Sweden, before opting to return to North America for the 2018–19 season, securing a one-year AHL contract with the Milwaukee Admirals on June 7, 2018.[10] Donovan instantly made an impact with the Admirals, leading the club in scoring with 12 points through his first 13 games before he was signed by NHL affiliate, the Nashville Predators, on a two-year, two-way contract on November 4, 2018.[11]
Nearing the conclusion of his contract with the Predators, Donovan opted to continue his tenure with the Milwaukee Admirals by signing a two-year AHL contract extension on March 23, 2020.[12]
With the Admirals opting out of playing in the pandemic delayed 2020–21 season, Donovan made a return to Sweden and the SHL, belatedly signing for the remainder of the season with HV71 on January 20, 2021.[13] He posted 2 goals and 7 points in 12 regular season games, unable to help prevent HV71 suffering relegation to the HockeyAllsvenskan (Allsv).
Returning to the Admirals for the following 2021–22 season, Donovan as an alternate captain, contributed with 8 goals and 40 points from the blueline in all 76 regular season games.
On June 17, 2022, Donovan again left the AHL and signed a one-year contract with German club, Adler Mannheim of the Deutsche Eishockey Liga (DEL).[14] In the 2022–23 season, Donovan as an alternate captain contributed offensively on the blueline with 8 goals and 23 points through 47 regular season games. He also added 8 assists in 12 playoff contests.
As a free agent, Donovan returned to North America after securing a one-year AHL contract with the Chicago Wolves on June 14, 2023.[15] In the 2023–24 season, Donovan continued to produce offensively from the blueline, totalling 43 points through 69 regular season games.
On August 26, 2024, Donovan concluded his 14-year professional career, after he was unveiled as an assistant coach of the Milwaukee Admirals of the AHL, affiliate to former club, the Nashville Predators.[16]
Donovan was a member of the United States junior hockey team that captured the gold medal in January 2010 at the 2010 World Junior Ice Hockey Championships with a 6–5 overtime victory against Team Canada.[17] Throughout the seven games Donovan gained three goals and two assists with a plus-6 rating.[18]