Adair was signed by the Baltimore Orioles out of Oklahoma State University on September 2, 1958 for a $40,000 bonus. He made his Major League Baseball debut with the club that day against the Washington Senators, coming into the game in the bottom of the 8th inning as a defensive replacement for shortstop Chuck Oertel. He did not get an at bat in the game. Adair's first big league at bat came on September 5 against the Boston Red Sox. After drawing a walk and scoring in the 8th inning, Adair reached base again in the ninth inning on a fielder's choice. He picked up his first big league hit in a 3–2 Orioles win over the visiting New York Yankees on September 21. That season, he hit.105 in 11 games with the Orioles, primarily playing shortstop. He hit.314 in 12 games in 1959 and went 1-for-5 in 3 games in 1960. Adair's first full season in the big leagues came in 1961 with the Orioles, hitting.264 with 9 home runs and 37 RBI in 133 games. Although the majority of his time was spent at second base, he also played some shortstop and third base that year. Once, during the 1964 season, he was struck in the mouth by a bad throw during the first game of a doubleheader with the Detroit Tigers. The resulting laceration required 11 stitches, but Adair was back in the park in uniform in time to play the entire second game. In 1965, 28-year-old Adair hit.259 with 7 home runs and a career-high 66 RBI in 157 games with the Orioles. He was among American League leaders with 157 games, 582 at bats, 26 doubles, 115 singles and 6 sacrifice flies. As a result, Adair finished 17th in the AL MVP vote that was won by Zoilo Versalles of the Minnesota Twins.
On June 13, 1966, Adair was traded by the Orioles with minor leaguer John Riddle to the Chicago White Sox for Eddie Fisher.
Boston Red Sox
On June 2, 1967, Adair was traded by the White Sox to the Boston Red Sox for Don McMahon and minor leaguer Rob Snow. Adair played well down the stretch with the Red Sox, hitting.291 with 3 homers and 26 RBI in 89 games, rounding out his season stats to.271 with 3 HR and 35 RBI in 117 games. With his pennant push performance at the plate, coupled with stellar defensive play, Adair finished 15th in the AL MVP balloting. Teammate Carl Yastrzemski won the award that year after claiming the elusive triple crown.
Kansas City Royals
Adair was taken by the Kansas City Royals with the 51st pick of the 1968 MLB expansion draft. In the Royals' inaugural season of 1969, the 32-year-old Adair hit.250 with 5 home runs and 48 RBI in 126 games. In 1970, Adair hit just.148 before being abruptly released on May 5 as he was about to board a plane to make a road trip to Baltimore with the team. Adair had spent much of spring training that year with a young daughter who had terminal cancer and eventually died and claimed the Royals let him go without taking the family's problems into consideration. Royals General Manager Cedric Tallis defended the team's decision to release Adair saying "We just felt he couldn't help the club".
Legacy
While having only a.254 career batting average, he was considered a good clutch hitter. However, his greatest strength was his defensive ability. Adair set then-major league records for single-season fielding percentage and fewest errors in 1964, and followed that up by leading the league in fielding percentage again in 1965. He also set a record for consecutive errorless games by a second baseman, and consecutive chances handled without an error from July 22, 1964 through May 6, 1965. In addition, he was considered a "gamer" who would often play when injured. After leaving Major League Baseball, Adair played in Japan for a year, and later coached for the Oakland Athletics and the California Angels, working under his former Oriole teammate and manager in Boston Dick Williams. Adair died of liver cancer on May 31, 1987 in Tulsa, Oklahoma, at the age of 50.
