Now in his fourth decade in Major League baseball, McKay says he only suited up for about a dozen games a year while growing up in British Columbia.
Small and lean as a teen, McKay was a talented shortstop, but few scouts visiting his region in the mid-to-late '60s were coveting infielders.
"Scouts were really looking for that one hard-throwing pitcher," he said.
Fortunately, McKay's older brother, Alex, recognized his potential.
"He loved baseball more than anyone I know," said McKay of his older brother. "He pushed me. I think he saw that I had a chance to play and the ability to play [at an elite level]."
It was Alex, who still lives in Vancouver, who instilled in McKay his legendary work ethic.
"I had so much respect for my older brother that it would upset me if he was disappointed in what I was doing," said McKay. "He was really helpful and kept me focused. And it got to the point where my work ethic is probably what has kept me around for so long as a coach. I just became the guy that worked harder than everyone else."
Now 58 years old, McKay is in better shape than many players. He's upbeat, energetic and modest, and has formed friendships with some of baseball's most storied and controversial characters -- including Billy Martin, Tony La Russa and Mark McGwire. His hard work has earned him considerable respect in the baseball fraternity.
Hard work also earned McKay a scholarship to Columbia Basin Junior College in Pasco, Wash., in 1969, where he starred for its baseball team for two years, before he was awarded another scholarship to Creighton University in Omaha, Neb.
Being a Canadian, McKay was not eligible for the First-Year Player Draft at that time. So after a year at Creighton, he decided to play summer ball in Wichita, Kan. On June 20, 1971, he inked a deal with the Minnesota Twins that included a $10,000 signing bonus.
After nearly four seasons in the Twins' Minor League system, McKay was called up by the big club in August 1975. Though he had been playing shortstop for Tacoma, the Twins' Triple-A affiliate, McKay was asked to replace third baseman Eric Soderholm at the Major League level.
Before McKay left for Minnesota, Tacoma player-coach Rick Renick, who had belted a home run in his first Major League at-bat, jokingly told the young Canuck that he expected him to do the same. So fittingly, on Aug. 22, 1975, McKay knocked the second pitch -- a slider from Tigers hurler Vern Ruhle -- in his first at-bat, out of the park.
"A blind squirrel finding a nut is all that was," said McKay modestly.
That home run ball now resides at the Canadian Baseball Hall of Fame in St. Marys, Ontario, and McKay remains the only Canuck to homer in his first big league at-bat.
The Vancouver native went on to hit safely in 21 of his first 22 Major League games and finished the season with a .256 batting average.
After another partial season with the Twins, McKay was selected by the Toronto Blue Jays in the 1976 Expansion Draft. Excited to be back in his home country, McKay was the only Canadian in the Jays' starting lineup in their first game on April 7, 1977.
"It was a really, really cold day," he said. "It was probably the coldest day I've ever played on. We had snow the night before and that morning they had to take the snow off the field. Everybody thought there was absolutely zero percent chance of playing, but they just said that this is such a big game that they wanted to play it."
The Jays defeated the Chicago White Sox, 9-5, in that inaugural contest and McKay recorded the game-winning RBI.
After two more seasons in Toronto, he signed with the Oakland A's in 1980, where he played for Billy Martin.
"A lot of people don't like Billy and a lot of people loved Billy," McKay said. "It seems like there's no in between. I'm one of the guys that really liked him. Billy would be hard on people if you didn't play the game right or if you didn't play the game hard. Those were two areas that I never had a problem with."
The volatile Martin transformed the A's from a laughingstock into contenders. Oakland finished with the best record in the American League in the strike-shortened 1981 campaign. In the postseason that year, McKay homered in the final game of the American League Division Series to help the A's defeat the Kansas City Royals. However, the New York Yankees defeated Oakland in the AL Championship Series.
After another season in Oakland, McKay spent the 1983 season as a player-coach in the A's Minor League system. He was hired as a coach by the big club in '84.
When La Russa was named the A's manager during the 1986 campaign, McKay retained his position with the club. He has now worked on La Russa's staff for 23 years, having moved with La Russa to St. Louis in '96.
"Tony gives everything to the game of baseball," said McKay. "He's just always thinking about the team, the team he's playing against, the team he's going to be playing against next week. He's always ahead of everybody else."
Working under La Russa, McKay has been a part of two World Series-winning teams.
"Obviously the World Series we won in Oakland in 1989 was the first time, and that was really exciting," McKay said. "We kind of redeemed ourselves for the year before when we got beat by the Dodgers."
But the 2006 championship with the Cards was equally sweet.
"We had five rookies on that team, and we had five released players, including Scott Spiezio, Preston Wilson, Jeff Weaver, Josh Hancock, Jorge Sosa and Jose Vizcaino," McKay said. "So to walk into that locker room and see all of these guys soaked in champagne, wrapped around a World Championship trophy, when just less than a month or so ago some of them had their hearts ripped out of their chests telling them they were released, was special."
A personal highlight for McKay was his induction into the Canadian Baseball Hall of Fame in 2001. With his brother, Alex, and wife, Lene, in the audience, McKay delivered a heartfelt and emotional speech.
That trip was one of his increasingly rare trips back to his homeland. While he remains patriotic, he says his Canadian relatives usually visit him at his home in Arizona.
McKay was asked to be part of the Canadian coaching staff at the 2009 World Baseball Classic, but declined due to his commitments with the Cardinals. That said, McKay would gladly consider a role with a Canadian team after he's done coaching at the big league level.
One question McKay is often asked is whether he has aspirations to be the first full-time Canadian Major League manager since George Gibson, who piloted the Pittsburgh Pirates in 1934.
"I really enjoy coaching," McKay said. "I really enjoy being on the field and working with the guys, and I think that's what I was destined to be. I just think I was made to coach, not manage."