Sustr never had to make a big splash en route to becoming a key part of the Lightning's defense.

Sustr left his hometown of Plzen, Czech Republic, at 18 for Kenai River, Alaska, and a stop in the North American Hockey League before joining Youngstown of the United States Hockey League. Sustr had yet to land on the radar of NHL scouts when he accepted a scholarship to the University of Nebraska-Omaha in 2010-11 at age 20.

Sustr continued to improve his skating while adding muscle. His strong hockey sense and growing feel for the game at each level of play drew the notice of scouts. By his junior season, Sustr attracted the attention of NHL teams eager to sign the 6-foot-7, 220-pound defenseman, who finished his collegiate career with 15 goals and 51 points in 111 games and earned All-Western Collegiate Hockey Association honors after his junior year.

He signed with Tampa Bay on March 21, 2013 and embarked on his pro journey, appearing in two games with the Lightning before being assigned to Syracuse of the American Hockey League. Sustr proved to be a valuable addition to Syracuse on its run to the Calder Cup Finals, appearing in all 18 playoff games, scoring twice with seven points and a plus-11 rating.

In 2013-14, Sustr appeared in 43 games with the Lightning, scoring his first goal against Dallas on April 5, 2014. With a full season of professional experience, Sustr became a regular with the Lightning for the 2014-15 season, appearing in 72 regular-season games and all 26 playoff games as Tampa Bay reached the Stanley Cup Final.

Sustr played top-four minutes for most of the season, gaining more trust from the coaching staff. He set career highs with four goals, 17 assists and 21 points.

Sustr played important minutes in the 2016 playoffs after Anton Stralman sustained a fractured leg. Sustr averaged more than 17 minutes per game, finishing tied for fourth among defensemen and 11th overall with a plus-7 rating.