Prior to making the NHL full-time in 2020-21, Nedeljkovic spent four seasons in the American Hockey League with the Charlotte Checkers from 2016-20, suiting up in 154 games with an 89-45-14 record, 2.57 goals-against average, 0.904 save percentage and 14 shutouts, while adding a 14-8 postseason record alongside a 2.25 goals-against average, 0.917 save percentage and two shutouts. His decorated AHL career included a 2019 Calder Cup championship with the Checkers, in which he led the AHL in wins (34) for a second-consecutive year and goals-against average (2.26) en route to winning the Baz Bastien Memorial Award as the league's top goaltender and earning a spot on the AHL First All-Star Team. Additionally, Nedeljkovic became the 13th goaltender in AHL history to score a goal during the 2017-18 campaign.
A native of Parma, Ohio, Nedeljkovic has several ties to the state of Michigan, notably as a teammate of Red Wings captain Dylan Larkin on the 2011-12 Belle Tire U16 team. Nedeljkovic went on to spend parts of three seasons with the Ontario Hockey League's Plymouth Whalers and one with the Flint Firebirds. In 191 OHL games with Plymouth, Flint and the Niagara IceDogs between 2012-16, Nedeljkovic posted an 89-77-20 record, 2.88 goals-against average, 0.918 save percentage and 10 shutouts. He was named the OHL's Goaltender of the Year in 2013-14 and earned back-to-back selections on the OHL Third All-Star Team the following two seasons. Nedeljkovic has represented the United States several times in international play, winning bronze at the 2016 IIHF World Junior Championship following a 4-2 record, 1.66 goals-against average and 0.943 save percentage, and leading his country to a gold medal at the 2014 IIHF World Under-18 Championship in which he led the tournament in goals-against average (1.84).