Lerg spent two seasons with the US National Development Program, then attended Michigan State for four seasons before turning pro. After two seasons in Springfield and a failed venture to Switzerland, Lerg landed with the Pens at the start of the 2010-11 season.
Lerg had a solid first season in Wilkes-Barre, recording 32 points (15+17) in 65 games, and followed that up by finishing second on the team with 53 points and tied for first with 27 goals in 2011-12. That performance put Lerg on the map, and he was picked up by the Colorado Avalanche and assigned to Lake Erie the next season.
Injuries limited Lerg to just 63 games over the next two seasons before the Sharks took a chance on the Michigan native prior to the 2014-15 campaign, signing him to a two-way deal.
After spending most of the regular season in Worcester, where he led the team with 41 points, Lerg received his first NHL recall by San Jose. He made his big league debut on April 9 against the Edmonton Oilers, and tallied the game-winning goal in a 3-1 win.