[citation needed] Karl played basketball at Boise State while majoring in Mass Communications.

Karl had weighed whether to return to college for his senior year or to enter the 2006 NBA draft, attending a few pre-draft workouts for various professional teams.

Karl made his NBA debut on October 30, 2007, with the Lakers versus the Houston Rockets, playing 37 seconds and registering no statistics.

On February 19, 2008, Karl joined Lakers' second-year guard Jordan Farmar as the only other player in league history to see action in same-day D-League and NBA games.

[5][6] In September 2009, Karl reached an agreement to attend training camp with the Cleveland Cavaliers, where he competed for a regular-season roster spot.

On October 22, 2009, the Cavaliers made three final cuts, ensuring Karl a spot on their opening day roster.

[12] In May 2011, after being relegated to the second division in Spain with CB Granada, he signed with Armani Jeans Milano in Italy until the end of the season.

[21] Westchester made significant improvement during the one season Karl spent on the bench, upping its record from 10–40 in 2014–15 to a 28–22 mark during the 2015–16 campaign.

On September 12, 2016, Karl took over his first head coaching role with the NBA D-League's Los Angeles D-Fenders, the affiliate team of the Lakers.