McGrattan was a fourth-round selection of the Los Angeles Kings (104th overall) at the 1999 NHL Entry Draft but never signed with the team.

[2] He began the 2001–02 OHL season as Mississauga's captain, but was traded to the Owen Sound Attack in October 2001, then to the Oshawa Generals a few days later.

[7] He attended the Detroit Red Wings' development camp prior to the 2001–02 season,[4] before signing a contract with the Ottawa Senators on June 2, 2002.

[8] Having established himself as an enforcer, and with the Senators seeking to add physical toughness to their lineup, McGrattan earned a spot on Ottawa's roster for the 2005–06 season.

McGrattan scored his first NHL goal on November 19, 2005, against goaltender Martin Brodeur of the New Jersey Devils, and led the league with 19 fights.

[2] McGrattan made headlines midway through the 2007–08 campaign when he fought teammate and goaltender Ray Emery – himself a noted fighter – in practice.

[10] McGrattan's on-ice performance had suffered over time in Ottawa as a result of a worsening drinking problem he had developed beginning early in his career with Binghamton.

[1] The Senators struggled late in the 2007–08 season, leading general manager Bryan Murray to make changes to the team.

[13] McGrattan's struggles with alcohol abuse reached its lowest point and he spent over two months at an Arizona rehab centre as he worked toward changing his life.

[1] He returned to the Coyotes late in the season but played only two additional games before he suffered a shoulder injury that required surgery to repair.

[15] He recorded his first career "Gordie Howe hat trick" – a goal, assist and fight – on October 16, 2009, in a 5–3 victory over the Vancouver Canucks.

[5] The Bruins traded him to the Anaheim Ducks, along with Sean Zimmerman, in exchange for David Laliberte and Stefan Chaput on February 27, 2011.

McGrattan scored 10 goals combined between Providence and Syracuse, the highest single-season total of his AHL career.

[23] McGrattan's positive influence in the locker room as a player always prepared to play was cited as a reason why Calgary re-acquired him.

[28] Leaving the Flames organization, McGrattan signed a one-year contract with the Anaheim Ducks,[30] and was subsequently assigned to the AHL's San Diego Gulls for the 2015–16 season.

[15] McGrattan's experiences led to a desire to help others; he works with the NHL substance abuse program to act as a mentor for others seeking the advice of a fellow player,[35] and plans to spend his off-seasons earning a university degree in addiction counseling.