Knowles was traded with Jackie Brandt to the Phillies for Jack Baldschun on December 6, 1965. He won the season opener against the St. Louis Cardinals, pitching six innings of one-run ball to earn his first career win. His first career save came on May 12 against the Los Angeles Dodgers. For the season, Knowles earned 13 saves. His 69 appearances, all in relief, were the third highest total of any pitcher in the league. At the end of his only season in Philadelphia, he was traded to the Washington Senators for Don Lock.
Washington Senators
Knowles began earning a reputation as a work-horse relief pitcher, as he was used 61 times by manager Gil Hodges in. He was used 32 times in when his season was cut short by President Lyndon B. Johnson's reserve call-up of the USAF's 113th Tactical Fighter Wing in which he was an airman first class. He returned to the Senators in May, and went 4–1 with four saves and a 2.01 ERA to earn his only career All-Star nod. Despite a 2–14 record in, Knowles enjoyed career highs in saves, appearances and innings pitched.
Knowles made five starts for the world champion A's in, pitching his only complete game shutout against the Boston Red Sox on August 14. The Athletics repeated as American League champions, and faced the New York Mets in the 1973 World Series. Knowles appeared in all seven games of the World Series, pitching 6.1 innings without giving up an earned run, and earning the saves in games one and seven. He is one of only two pitchers to appear in all seven games of a World Series. Knowles had an off year in, going 3–3 with a 4.22 ERA and blowing two of his five save opportunities. His.296 batting average against was the highest in the Oakland bullpen. Regardless, the A's won their third World Series in a row in ; however, Knowles did not make a post-season appearance. Shortly after the World Series, he, Bob Locker and Manny Trillo were dealt to the Chicago Cubs for Billy Williams.
Final years
Knowles inherited the closer's role in Chicago, saving 15 in and nine in. Shortly before spring training, Knowles was dealt to the Rangers for a player to be named later and cash. He went 5–2 with a 3.22 ERA and four saves to help the Rangers to a second-place finish. After the season, he was reunited with his former A's manager Dick Williams when his contract was sold to the Expos. He appeared in 60 games with the Expos, going 3–3 with six saves and a 2.38 ERA. Knowles did not enjoy playing in Canada, citing taxes, language problems and political unrest in Quebec as the reasons for his displeasure. After just one season in Montreal, Knowles signed a two-year deal with his home team Cardinals. Knowles made 48 appearances and earned six saves with the Cards in. He made just two appearances in April before retiring and accepting a coaching position in the Cardinals' farm system. At the time of his retirement, he was tied for 13th in career saves. In between, Knowles played winter ball with the Tiburones de La Guaira club of the Venezuelan League in the 1964–1965 season, where he posted a 13-9 record with a 2.37 ERA and 155 strikeouts to earn Triple Crown honors.
Coaching career
After eight years as a minor league pitching coach for the Cardinals, Knowles was hired as the Philadelphia Phillies' pitching coach in January by new manager Nick Leyva. Under Knowles, the Phillies' pitching staff, which had a National League worst 4.14 ERA and 628 walks in 1988, showed only mild improvement, and he was demoted to a minor league coaching position after the season. On January 13, 2014, Knowles was named as the pitching coach for the Toronto Blue Jays Single-A affiliate Dunedin Blue Jays.