Milwaukee / Atlanta Braves (1964–1983)
Niekro debuted with the Milwaukee Braves in 1964, working 15 major league innings and spending time with the team's class AAA minor league affiliate. He stayed with the major league team all year in 1965, pitching 74+2⁄3 innings in 41 games and recording six saves. In 1966, Niekro split time again between the Braves and their minor league system, going 4–3 with a 4.11 earned run average (ERA).
Niekro led the league with a 1.87 ERA in 1967, earning an 11–9 record with 10 complete games and 9 saves. He began the year as a relief pitcher but had earned a job in the starting rotation during the season.
Before the 1968 season, sportswriter Fred Down described the Braves' pitching staff as "chaotic" and reported that team leadership was planning to use Niekro as both a starter and a reliever in the coming season. He appeared in 37 games, finishing with a 14–12 record and 15 complete games. He appeared in relief three times, earning two saves.
In 1969, his first All-Star season, he had a 23–13 season with a 2.56 ERA, finishing second in the National League Cy Young Award balloting to Tom Seaver. The Braves went to the playoffs, where Niekro was 0–1 with four earned runs allowed in an eight-inning appearance against the New York Mets. Niekro's playoff loss came against Seaver. The team was eliminated from the playoffs after losing the next two games.
In 1970, he went 12–18 with a 4.27 ERA in what turned out to be a down year. He surrendered a league-leading 40 home runs that year, a feat he would not repeat until 1979.
From 1971 to 1973, he combined for a record of 44–36. The Braves finished 3rd, 4th, and 5th in their division. On August 5, 1973, Niekro threw a no-hitter against the San Diego Padres, the first for the Braves since moving to Atlanta.
In 1974, Niekro led the league in several pitching categories, including wins (20), complete games (18), and innings pitched (302.1). He finished third in the voting for the Cy Young Award that year.
From 1975 to 1976, he went 15–15 and 17–11 and made a second All-Star appearance in 1975.
Between 1977 and 1979, Niekro was the league leader in complete games, innings pitched and batters faced. In 1979, the 40-year-old Niekro led the league in both wins (21) and losses (20). He finished sixth in Cy Young Award voting in both 1978 and 1979, and made his third All-Star appearance in 1978, as well as winning three consecutive Gold Glove Awards from 1978 to 1980.
Phil and Joe Niekro were NL co-leaders in wins in 1979; the two brothers each earned 21 wins that year. As of 2013, he remains the last MLB pitcher to win and lose 20 games in the same season. The 1979 season was Niekro's third and final 20-win season and his second and final 20-loss season.
In 1980 and 1981, he went 15–18 and 7–7 while leading the league in games started (38) and losses (18) in 1980.
In 1982, at the age of 43, Niekro led the Braves with a 17–4 season while winning his fourth Gold Glove Award and appearing in his fourth All-Star game. On October 1, with the Braves clinging to a one-game lead over the Los Angeles Dodgers, Niekro beat the San Diego Padres almost single-handedly by throwing a complete game shutout and hitting a two-run home run. Niekro started Game One of the subsequent 1982 National League Championship Series against the St. Louis Cardinals and pitched well, but the game was called on account of rain just before it became official. He pitched six innings of Game 2 and left with a 3–2 lead. However, the Cardinals scored two late runs after Niekro left the game and would eventually sweep the series.
In 1983, he went 11–10 and won his fifth Gold Glove Award. After the season, the Braves released him.
