1974, the Royals announced Boros was being elevated to the major league club to replace Charley Lau on the team's coaching staff for the 1975 season. He was the Royals third base coach in 1975 under manager Whitey Herzog. From 1976 to 1979, he was the Royal's first base coach and was "credited with helping the Royals develop an aggressive baserunning style." While Boros was in Kansas City, he began to attract media attention for his "scientific approach" to baseball. In July 1977, the UPI published a feature story about Boros in which it observed: Boros began putting a book together on all the pitchers and catchers in the American League last year, noting their strengths and weaknesses and any tipoffs that might give Royals runners an edge on the basepaths. His observations were written into a small 25-cent notepad along with a flock of stopwatch readings that represent the time it takes a pitcher to throw the ball to home plate out of both the stretch and windup, and how long it takes a catcher to peg the ball to second and third base. Boros also studied pitchers, looking for tipoffs they intended to throw to first base. He said, "There's always some tipoff. The head, the shoulder, the hip, the knee, the toe – every pitcher has something that gives away his pickoff move. When you find it, you've got the upper hand on the base baths." With the benefit of Boros' scientific approach, the Royals led the American League in stolen bases in both 1978 (216) and 1979 (207). The 1978 team had eight players (led by Willie Wilson, Freddie Patek, Amos Otis, George Brett, and Hal McRae) who stole at least 10 bases and won the American League West pennant with a record of 92–70. Montreal Expos In 1980, Boros was hired by the Montreal Expos organization and managed the Calgary Expos. During the 1981 and 1982 seasons, he was the first base coach for the Montreal Expos. Boros was hired by the Expos in part due to his reputation as one of the best coaches in baseball at teaching base stealing technique. His San Jose team set the modern minor league record with 372 stolen bases, and the Royals led the American League in stolen bases during his tenure there. During Boros' two seasons as the Expos first base coach, Tim Raines became the leading