McDonald was first coached by his father, who originally had him play defence, but moved him to forward when it became evident he would be too small to make a career as a defenceman.

McDonald spent the 2004–05 lockout season playing overseas in the Deutsche Eishockey Liga with team ERC Ingolstadt, along with fellow NHLers Marco Sturm, Jamie Langenbrunner, and Aaron Ward.

On January 19, 2007, McDonald was selected to play in his first NHL All-Star game, replacing Detroit Red Wings forward Henrik Zetterberg who was injured.

During the skills competition, McDonald won the fastest skater challenge, finishing with a time of 14.03 seconds (Dylan Larkin holds the record of 13.172).

On December 14, 2007, in order for the Anaheim Ducks to free up salary cap space for Scott Niedermayer, McDonald was traded to the St. Louis Blues for Doug Weight.

[3] McDonald would finish the 2008–09 season with 15 goals and 29 assists for 24 points in 46 games while the Blues as a team would finish the season as the sixth seed in the Western Conference to earn a spot in the 2009 playoffs, marking the first time since 2004 where the Blues clinched a playoff spot, where they would be swept in the first round by the third-seeded Vancouver Canucks.

On November 30, 2010, in a 7–5 loss to the Chicago Blackhawks, McDonald was the subject of a controversial boarding incident on Blackhawks' forward Viktor Stålberg towards the end of the game and was given a minor penalty for the play but ultimately was not suspended and/or fined by the NHL most likely due McDonald not having a suspension history and Stålberg being able to get back on his feet on his own power having not been injured on the play despite being in discomfort.

McDonald announced his retirement on June 6, 2013, citing concussion issues in his early years in the NHL as the main reason for his decision.