Jenkins never received the fame his accomplishments warrant. He racked up 284 victories, had six consecutive 20-win seasons paired with 200-plus strikeouts, pitched more than 300 innings five times, and is high on the all-time strikeout list with 3,192. He never pitched on a pennant winner, though, and was usually on teams that were known more for hitting than pitching.
When the Cubs acquired Jenkins midway through the 1966 season, manager Leo Durocher converted the hard-throwing 6’5″ 200-lb righthander into a starter. Beginning in 1967 and continuing through 1972, Jenkins won at least 20 games every year. He set a modern Cubs record with 236 strikeouts in 1967, then raised the record each of the next three seasons to 260, 273, and 274. In the 15-inning 1967 All-Star game, Jenkins equaled Carl Hubbell‘s 1934 strikeout numbers, fanning six in three innings, but he gave up a sixth-inning homer to Brooks Robinson that tied the score at 1-1. He gave up another homer, to Harmon Killebrew, in his only other All-Star appearance (1971). He led the NL in 1971 with a 24-13 record with 263 strikeouts, a 2.77 ERA, and 30 complete games to win the Cy Young award. He also hit .243 with six homers.
After failing to win 20 games in 1973, and because of Ron Santo‘s diminishing skills at third base, the Cubs traded Jenkins to the Texas Rangers for Bill Madlock. In his first start in a Ranger uniform, he shut out the World Champion A’s on one hit. He led the AL with a 25-12 record, the seventh and last time he would win 20 games. He fell to 17-18 in 1975 and was traded to Boston. He was going to Fenway Park with high expectations for 1976, joining a Red Sox team that had come within one win of a world title the previous year. But the fire had gone out of Jenkins’s arm. He could not win more games than he lost. By late 1977, Red Sox manager Don Zimmer was fed up with Jenkins’s inconsistency and banished him to the bullpen. On September 18 in Baltimore, Brooks Robinson Night, Jenkins supposedly fell asleep (Jenkins said he simply had his feet up in the cart) in the bullpen and had to be woken up to warm up. Zimmer was livid, and Jenkins didn’t pitch again in a Boston uniform. At the end of the year, Jenkins headed back to Texas, where he partially regained his form and won 18 games. Jenkins was reacquired by the Cubs in 1982 and led the club in innings pitched and ERA with a 14-15 record at the age of 38.