Junker was drafted by the Detroit Lions in the fourth round (48th overall pick) of the 1957 NFL Draft. As a rookie in 1957, he caught 22 passes for 305 yards and four touchdowns in the regular season. He then blossomed in the playoffs. In the divisional playoff against the San Francisco 49ers, Junker caught eight passes for 92 yards, one of them for a touchdown. In the 1957 NFL Championship Game, he was the Lions leading scorer with 12 points and caught five passes, including touchdown receptions covering 26 and 23 yards.