Richards played 11 National Hockey League (NHL) seasons, spending time with the Philadelphia Flyers, Los Angeles Kings, and Washington Capitals.

He played level A rep hockey for the Kenora Thistles until being drafted fourth overall in the 2001 OHL Priority Selection by the Kitchener Rangers.

[2] After receiving a tip from a friend in Kenora, Rangers general manager Jamie MacDonald traveled to see Richards play on two occasions.

In his last season of junior, 2004–05, he embarked on another Memorial Cup run with Kitchener, but despite a remarkable 28-point performance from Richards in just 15 playoff games, the Rangers were eliminated by the London Knights in the OHL semi-finals.

As soon as Kitchener was eliminated, the Flyers assigned Richards to the Philadelphia Phantoms, their American Hockey League (AHL) affiliate, for their playoff run.

Recognizing his ascent as a leader on the team, Richards was named one of the Flyers' alternate captains at the outset of the season[8] and was signed to a lengthy 12-year contract extension worth $69 million on December 13, 2007.

[11] In doing so, he became just the second player in NHL history to score his first playoff goal on a penalty shot (the first was Wayne Connolly who did so with the Minnesota North Stars in 1968).

[12] The Flyers defeated the Capitals in seven games and then upset the Montreal Canadiens before falling to the Pittsburgh Penguins in the Eastern Conference Finals.

[13] On February 15, 2009, Richards became the first player in NHL history to score three career three-on-five short-handed goals when he beat New York Rangers goaltender Henrik Lundqvist in a 5–2 win.

[14] Six days later, on February 21, Richards became the first Flyer in team history[citation needed] to score a short-handed goal in three consecutive games and the first NHL player to do so since Joe Sakic in 1998.

[15] Facing the Pittsburgh Penguins for the second consecutive year in the 2009 playoffs, Richards added five points in six games, but could not help the Flyers from being eliminated.

After Richards' season ended, he was announced as a finalist for the Frank J. Selke Trophy, awarded to the NHL's top defensive forward, along with Pavel Datsyuk of the Detroit Red Wings and Ryan Kesler of the Vancouver Canucks.

He issued a verbal boycott against the media in October 2009 after he was asked if the trade of forward Joffrey Lupul to the Anaheim Ducks was the result of a partying lifestyle that many players on the team were accused of sharing.

[19] Accusations of team players drinking and partying excessively continued throughout the season, specifically with Richards and Jeff Carter.

Richards scored 23 goals to go along with 43 assists during the 2010–11 season as the Flyers earned the second seed in the Eastern Conference, and played the Buffalo Sabres in the first round of the 2011 playoffs.

Richards and Carter were reportedly traded due to their long contracts and to clear up cap space for Ilya Bryzgalov.

On June 13, 2014, Richards became a Stanley Cup champion for the second time when the Kings defeated the New York Rangers 3–2 in double overtime in Game 5.

"[32] The termination resulted from an incident at the US-Canada border in which Royal Canadian Mounted Police arrested Richards for possession of oxycodone, a controlled substance, without a prescription.

[33][34] On August 10, it was announced that the National Hockey League Players' Association (NHLPA) had filed a grievance on behalf of Richards to contest the termination.

The following year, Richards returned to the World Juniors as team captain and led Canada to its first gold medal at the tournament since 1997.

On December 30, 2009, Richards was selected to play as a member of Team Canada at the 2010 Winter Olympics in Vancouver, British Columbia.