Nelson started his career with a 4-0 record for the Pirates in 1970, a feat not equaled by a Pirates starting pitcher until Zach Duke in 2005.[3] Nelson also was the last Pirate pitcher to win his first 3 career starts until Gerrit Cole matched the feat in 2013.[4]
Nelson also was the starting and winning pitcher in the final game played at Forbes Field on June 28, 1970. He commented on the fans' frenzy at the end of that game: "After the game, the fans stormed the field and took everything, grass, bases, numbers off the scoreboard. I even saw some old ladies with parts of chairs. It was a real scene."[5]
Nelson appeared in 15 games for the Pirates in 1970 and 17 games in 1971, both as a starter and a reliever. He struggled with control in 1971, walking 26 batters in 34 innings.[6] In July, he was demoted to the minor leagues, but refused to report to his minor-league team. Although his teammates voted him a half-share of their 1971 World Series money, Pirates management did not award him a World Series ring.[7] He underwent rotator cuff surgery and never returned to the majors.[7]