Wishart entered junior hockey after being selected in the second round, twenty-fourth overall, by the Prince George Cougars in the 2003 WHL Bantam Draft. Wishart did not appear for Prince George, however, until the 2004-2005 season where he had 1 goal and 8 points in 58 games to go with 41 penalty minutes. In 2005-2006, he posted 5 goals and 37 points in 70 games en route to being named the twenty-first best North American skater prospect for the 2006 NHL Entry Draft by NHL Central Scouting. Wishart was selected sixteenth overall in the 2006 NHL Entry Draft by the San Jose Sharks and returned to junior for the 2006-2007 season. That year he posted 11 goals and 49 points in 62 games for the Cougars. After growing increasingly frustrated with the lack of talent around him in Prince George, Wishart was traded midway through the 2007-2008 season to Moose Jaw. Between the Cougars and Warriors, Wishart put up 16 goals and 67 points in 72 games before going scoreless in 5 games for Worcester of the AHL at the end of the season. In the summer of 2008, Wishart was traded to Tampa Bay as a part of the deal that sent Dan Boyle to San Jose. He played in 61 games for the Lightning's AHL affiliate, the Norfolk Admirals, scoring a modest 1 goal and 7 points in 61 games. He also, however, posted the best plus/minus rating of any regular defenseman on the team with a +5 rating. He also made his NHL debut on January 22, 2009 against the Carolina Hurricanes and ended up with 1 assist in 5 games at the NHL level.