Johnson threw and batted right-handed, and was listed as 6 feet 2 inches (1.88 m) tall and 190 pounds (86 kg). He signed his first pro contract with the Boston Braves' organization in 1949 and missed the 1952 and 1953 seasons performing military service in the Korean War. He was 28 years old when he received his first MLB opportunity in the closing weeks of the 1959 Cubs' season, working in four games with two starts. In those starting assignments, against the Cincinnati Reds on September 10 and the Pittsburgh Pirates six days later, he went a total of ten innings pitched and allowed only three earned runs. Chicago won both contests, but Johnson was not involved in either decision. He began 1960 with the Cubs and appeared in 17 games through June 12, all in relief, picking up two wins and one save. He spent the rest of the year with the Triple-AHouston Buffs.