He threw and batted left-handed, stood 6 feet 4 inches (1.93 m) tall and weighed 205 pounds (93 kg).

As a "bonus baby", the 18-year-old Leja was forced by the regulations of the day to spend the first two seasons of his professional baseball career on a Major League roster.

[2] After finally being allowed to play regularly in minor league baseball, Leja showed his ability as a strong power hitter, exceeding the 20-home run mark from 1957 to 1959 and again in 1961, however, the Yankees never recalled him, then traded him to the St. Louis Cardinals after the 1961 season.

The Angels, in their second season as an American League expansion team, then purchased Leja's contract during spring training in 1962, where he made the team's early-season 28-man roster and appeared in seven more games, including four starts at first base, although going hitless (with just one base on balls) in 16 at bats.

Leja died of a heart attack in Boston at age 55 and was interred in Greenlawn Cemetery in suburban Nahant, Massachusetts.