Gersich, a native of Chaska, Minnesota, has some good hockey bloodlines. He's the nephew of Neal Broten, Aaron Broten and Paul Broten, each of whom played in the NHL during the 1980s and 1990s.

The Washington Capitals selected Gersich, a forward, in the fifth round (No. 134) of the 2014 NHL Draft and signed him to a two-year entry-level contract on March 23, 2018, after his junior season at the University of North Dakota, where he had 29 points (13 goals, 16 assists) in 40 games.

Gersich finished his college career with 77 points (43 goals, 34 assists) in 117 games. His biggest goal came as a freshman in 2016, when he scored in North Dakota's 5-1 victory against Quinnipiac in the national championship game.

Gersich made his NHL debut against the New York Rangers on March 28, 2018. He had one assist in three regular-season games with Washington and got into two playoff games for the Capitals during their run to the 2018 Stanley Cup.