14. John Mayberry

John Mayberry arrived in Kansas City as the first true home run threat for a young franchise, a massive left-handed presence who provided the lineup with an immediate injection of power. For six seasons, he was the primary engine of the Royals' offense, a player whose ability to drive the ball over the fence was matched only by a specialized eye for the strike zone that kept him among the league leaders in on-base percentage.

Mayberry had an immediate impact in 1972 after a lopsided trade with Houston. He reached a career-defining breakout in his debut season with the club, winning the Royals Player of the Year honors and signaling a transition from a young prospect to a premier American League slugger. He possessed a focused intensity at the plate, pairing his strength with a disciplined approach that saw him lead the league with a .417 on-base percentage in 1973. He showed the organization that a first baseman could be both a high-frequency home run threat and a master of the walk, setting a franchise record with 122 free passes that still stands today.

The best season in Kansas City came during the 1975 campaign. That summer, Mayberry became the first player in franchise history to cross the 30-homer threshold, finishing with 34 home runs and 106 RBIs. His performance earned him a runner-up finish for the American League MVP, as he led the league in walks for a second time while recording a career-high 38 doubles. He provided the dependable, day-to-day production that transformed the Royals into a perennial contender, eventually recording three seasons with at least 100 RBIs. Despite his offensive efficiency, his defensive range at first base remained a difficult hurdle that often limited his overall statistical value.

The story in Kansas City took a sudden and turbulent turn during the 1977 postseason. Following a regular season where he hit 23 home runs and hit for the cycle, Mayberry fell out of favor with manager Whitey Herzog. A late arrival before Game 4 of the ALCS against the Yankees led to a benching that effectively signaled the end of his tenure. He was subsequently sold to the Toronto Blue Jays before the 1978 season, leaving the Royals with 143 home runs and 552 RBIs.

In 1996, the Royals inducted him into their Hall of Fame.