MacKay enjoyed a 20-year career as both a top amateur and a professional tennis player. He started in the early 1950s as the Ohio high school tennis champion. From there, he attended the University of Michigan. He won five Big Ten Conference championships while at Michigan -- singles championships in 1956 and 1957, and doubles championships (with partner Richard Potter) in 1955, 1956, and 1957. In June 1957, MacKay won the NCAA singles title to help the Wolverines clinch their first and only national team championship. He was the first Big Ten player to win the NCAA tennis singles title. MacKay was also the first Michigan player to be named an NCAA All-American. He made five U.S. Davis Cup appearances (1956, 1957, 1958, 1959 and 1960) and was part of the 1958 Davis Cup championship team. In 1960, he had the No. 1 U.S. ranking. He spent three years on the pro tour from 1961-1963.
Since the 1970s, MacKay has been a tennis broadcaster. Over his 30-year broadcasting career, MacKay has teamed him with Arthur Ashe, Bud Collins, Beth Herr, Leif Shiras, among others and has become the voice U.S. fans tuned to for events such as the US Open, Wimbledon and ATP tennis. He currently provides color commentary, play-by-play and lead analysis for The Tennis Channel's coverage of the top tennis tournaments in the world. He has also provided color commentary on the Fox Sports Network. MacKay will serve as the play by play announcer for NBC Sports coverage of Tennis at the 2008 Summer Olympics.
MacKay has also served as tournament director and promoter for more than 12 annual events, highlighted by promoting two U.S. Davis Cup finals. As president of BMK Sports, MacKay is on the Board of Directors for Youth Tennis Advantage in Northern California. MacKay ran what is now the SAP Open from 1970 until 1995.
Interviewed in 2007, MacKay recalled his playing career: "I won the NCAAs in Salt Lake City in June of 1957. I unfortunately missed my graduation at Michigan Stadium because of it, but I got my diploma eventually. Then I played amateur tennis. In those days, there were two games – there was professional tennis and there was amateur tennis – and there was no open tennis as we know it today. I played amateur tennis for the next three summers and represented the United States on our Davis Cup team. I actually played my first Davis Cup match while I was still at Michigan in the summer of 1956. The United States won the Davis Cup in 1958 in Australia, and I was ranked No. 1 in the United States in 1960, and then I turned professional. In those days, that meant you went onto the Jack Kramer Tour because that was the only professional tour. That was where we played across the country and across the world. I signed a professional contract with Kramer and played pro tennis from 1961-63. Since there really wasn’t a future in professional tennis in those days, I migrated to California in 1964. I actually started working for Jack Kramer in what was then called the International Professional Tennis Tour. I’ve been in California ever since. I worked with Jack through the late 60’s. In 1970, I took over what was called the Pacific Coast Championships in Berkeley, here in Northern California. Our first winner was Arthur Ashe; our next winner was Rod Laver. After that, the tournament became the major tennis event in Northern California. I started my own company in ’73 called BMK Sports, and that company now puts on the major event of the year. Plus, I did a lot of television commentary and that sort of thing. It all fits under one big umbrella."