[2] He split his professional rookie season between Anaheim and their American Hockey League (AHL) affiliate, the Cincinnati Mighty Ducks.

He went on to help the Ducks advance through the playoffs, past the Minnesota Wild, Vancouver Canucks, and Detroit Red Wings, en route to a Finals victory against the Ottawa Senators to capture both his and the franchise's first Stanley Cup championship.

Kunitz had been injured during the semi-finals against the Red Wings, but returned late in the Stanley Cup Finals against Ottawa to help clinch the championship in game five.

In regards to Kunitz' new position, Ducks head coach Randy Carlyle explained, "Rob Niedermayer was an alternate last year and did a fine job, and we thought it was important to involve our younger players in the leadership role.

In the midst of another slow season in 2008–09, he was traded to the Pittsburgh Penguins along with prospect Eric Tangradi for defenceman Ryan Whitney.

The Penguins faced off against the Nashville Predators in the 2017 Finals, defeating them in six games to successfully defend the Stanley Cup, with Kunitz assisting on the series-winning goal.

[6] On July 1, 2017, Kunitz left the Penguins as a free agent and signed a one-year, $2 million, contract with the Tampa Bay Lightning.

Kunitz recorded 13 goals and 29 points during the season, but just one assist in the playoffs as the Lightning lost in the Eastern Conference Final to the eventual champion Washington Capitals in 7 games.

He joined the Blackhawks' organization as a player development adviser as well as the coaching staff of their American League affiliate, the Rockford IceHogs.

Kunitz admitted that during his first visit, he had a low-key celebration at Riffel as a result of teammate Ryan Getzlaf's profile.