In his Major League debut on April 12, against the Cincinnati Reds at Dodger Stadium, Richert set a record by striking out the first six batters he faced. He entered the game with two outs in the top of the second inning with his Dodgers trailing 4–0, and struck outVada Pinson for the final out. Richert then recorded a four-strikeout third inning in which his victims were Frank Robinson, Gordy Coleman, Wally Post and Johnny Edwards; his record-tying sixth strikeout was of Tommy Harper leading off the fourth., Richert is the only pitcher to record a four-strikeout inning in his Major League debut. He also set a Major League record by retiring 12 consecutive batters, the most by a pitcher making his MLB debut as a reliever; Max Scherzer would break this record in by retiring 13 consecutive batters. Richert won the game in 3 innings of relief, giving up no hits or walks and striking out seven. That year, he went 5–4 as a spot starter in a rotation led by the futureHall-of-Fame duo of Don Drysdale and Sandy Koufax. In, he went 5–3 on a Dodger team that won the World Series; Richert did not pitch in the Series, which the Dodgers swept from the New York Yankees. After the season, Richert, Frank Howard, Ken McMullen, Dick Nen and Phil Ortega were traded to the Washington Senators for fellow pitcher Claude Osteen, infielder John Kennedy and $100,000 cash. Richert's two full seasons with the Senators, and, were the two best seasons of his career. In the former he won a career-high 15 games with a 2.60 earned run average, also a career high. In the latter he went 14–14 with a 3.37 ERA and set a career-high with 195 strikeouts. He struck out seven consecutive batters in an April 24 game against the Detroit Tigers in the latter year, but still lost, 4–0. Richert was also an All-Star during both seasons and was the losing pitcher in the 1966 game, giving up a single to ex-Dodger teammate Maury Wills, which scored Tim McCarver for the winning run in the 10th inning. After going 2–6 to start the season, Richert was traded to the Baltimore Orioles in a deal that sent Mike Epstein to Washington. Richert went 7–10 as an Oriole in this, his final season as a starter. In he went 6–3 with a 3.47 earned run average in his first season as a relief pitcher. Richert pitched on an Oriole team that played in three consecutive World Series from to. In 1969 he went 7–4 with 12 saves and a 2.20 ERA. The Orioles lost the World Series in surprising fashion to the New York Mets, and Richert was involved in a controversial play that ended Game 4. In the bottom of the 10th, with the game tied at 1–1, J. C. Martin laid down a bunt and was hit by Richert's throw; the error allowed Rod Gaspar to score the winning run from second. Television replays later showed that Martin was running inside the baseline, which could have resulted in him being called out for interference. In, Richert went 7–2 with 13 saves and a 1.98 ERA. He was a member of the championship team that year, the Orioles defeating the Cincinnati Reds in five games. Richert saved Game 1 of that Series in relief of Jim Palmer. During a 13-year baseball career, he compiled 80 wins, 925 strikeouts, and a 3.19 earned run average.
