[1] In 2009–10 Ritchie scored 13 goals and 16 assists in 65 games for the Sarnia Sting during his first season in the Ontario Hockey League (OHL).

[8] A As the Texas Stars qualified for the 2013 Calder Cup playoffs, Ritchie scored the game-winning goal of Game 1 of the Western Conference Quarterfinal against the Milwaukee Admirals on April 27, 2013.

[13] Ritchie began the season strong, tallying two goals and seven assists to tie for ninth among AHL rookies in scoring by early November.

[20] Ritchie subsequently missed the first eight games of the playoffs before returning to the lineup for the Western Conference Semi-Finals against the Grand Rapids Griffins.

In his return, he scored a goal on the power play to lift the Stars 7–1 over the Griffins and advance them to the Western Conference Finals.

[20] Following their Calder Cup win, Ritchie returned to the Dallas Stars' training camp and participated in his second NHL Prospect Tournament in Traverse City, Michigan.

[25] Although the Stars won their game against the Carolina Hurricanes prospects, Ritchie injured his right pinky and was expected to remain out for the remainder of the tournament as a precaution.

[26] After spending two weeks in recovery, Ritchie returned to the Stars lineup for their third exhibition game against the Tampa Bay Lightning on September 26.

[33] Ritchie subsequently scored the game-winning goal in his NHL debut as the Stars shutout the Arizona Coyotes 6–0 on January 1.

[35] He earned playing time on the Stars' top line with Tyler Seguin and Jamie Benn[36] as he tallied three goals in his first six NHL games.

[38] However, this was shortlived as Ritchie suffered an undisclosed injury and was placed on injured reserve prior to the 2015 NHL All-Star Game break.

[45] He helped the Texas Stars qualify for the 2015 Calder Cup playoffs and tied for the team lead in scoring before they were eliminated by the Rockford IceHogs.

[51] In his NHL postseason debut, Ritchie played an average of 6:36 through 11 shifts during the Stars' Game 4 win over the St. Louis Blues.

[62] After seven seasons within the Stars organization, on June 25, 2019, Ritchie was not tendered a qualifying offer enabling him to become an unrestricted free agent on July 1.

[63] Marking his 26th birthday on the opening day of free agency, Ritchie was signed to a one-year, $1 million contract with the Boston Bruins.

[71] After impressing at training camp, Ritchie signed a one-year, two-way contract with an average annual value of $700,000 with the Calgary Flames on January 17, 2021.

[citation needed] On November 18, 2023, Ritchie signed a one-year contract with HC Dinamo Minsk of the Kontinental Hockey League (KHL).

According to Nitra club president Miroslav Kováčik, the reason for his release was that Slovak league officiating did not allow Ritchie or other skilled players to fulfill their offensive potential.

During the 2012–13 season, Ritchie played with Team Canada to win gold medals at both the 2012 Ivan Hlinka Memorial Tournament and the 2013 IIHF World U18 Championships.