Mike Sweeney's journey in Major League Baseball began when he was drafted by the Kansas City Royals in the 10th round of the 1991 MLB Draft. Initially, he played as a catcher, but his career took a turn when he transitioned to first base, a move that would define much of his time in the majors. Sweeney made his MLB debut with the Royals in 1995, and over the years, he became a central figure in their lineup.

Sweeney's offensive skills were evident early on, and he quickly became known for his ability to hit for both average and power. His breakout season came in 1999 when he hit .322 with 22 home runs and 102 RBIs. This performance earned him his first All-Star selection, an honor he would receive five times during his career. Sweeney's consistency at the plate was a bright spot for the Royals during a period when the team struggled to find success in the standings.

Throughout his career, Sweeney was recognized for his leadership both on and off the field. He was often seen as a mentor to younger players and was respected by teammates and opponents alike. His sportsmanship and character were acknowledged when he received the Hutch Award in 2007, an award given to a player who best exemplifies the fighting spirit and competitive desire of Fred Hutchinson.

Injuries, however, were a recurring challenge for Sweeney. Despite his talent, he faced several setbacks that limited his playing time, particularly in the latter part of his career. These injuries often kept him from maintaining the level of performance he displayed in his peak years.

After leaving the Royals in 2007, Sweeney played for several other teams, including the Oakland Athletics, Seattle Mariners, and Philadelphia Phillies. His time with these teams was marked by a reduced role, often serving as a designated hitter or a bench player. Despite this, he continued to contribute whenever possible and remained a respected veteran presence in the clubhouse.

Sweeney's career came to a close after the 2010 season. He retired with a .297 career batting average, 215 home runs, and 909 RBIs. His legacy in Kansas City remains strong, as he is remembered as one of the franchise's most beloved players. In recognition of his contributions to the team, Sweeney was inducted into the Kansas City Royals Hall of Fame in 2015.