Danny Duffy, a left-handed pitcher, spent his entire Major League Baseball career with the Kansas City Royals. Drafted by the Royals in the third round of the 2007 MLB Draft, Duffy made his major league debut on May 18, 2011. His early years in the majors were marked by a blend of promise and challenges, as he navigated the transition from the minors to facing top-tier hitters.

Duffy's pitching style was characterized by a fastball that could reach the mid-90s, complemented by a curveball and changeup. This repertoire allowed him to be an effective starter for the Royals, although his career was intermittently hampered by injuries. In 2012, he underwent Tommy John surgery, which sidelined him for the remainder of that season and a significant portion of 2013. Despite this setback, Duffy returned to the mound with determination, gradually re-establishing himself as a reliable option in the Royals' rotation.

The 2014 season was a turning point for Duffy. He posted a 2.53 ERA over 149.1 innings, helping the Royals reach the postseason for the first time since 1985. Although he primarily pitched out of the bullpen during the playoffs, his contributions were vital to the team's success. The Royals advanced to the World Series, ultimately falling to the San Francisco Giants in a hard-fought seven-game series.

Duffy's role in the Royals' 2015 campaign was equally important. He started 24 games during the regular season, contributing to the team's strong performance that led to another postseason appearance. This time, the Royals captured the World Series title, defeating the New York Mets in five games. Duffy's ability to adapt, whether as a starter or reliever, proved beneficial throughout the season and playoffs.

In the years following the Royals' championship, Duffy continued to be a mainstay in the rotation. The 2016 season was particularly noteworthy for him, as he achieved career highs in wins and strikeouts. On August 1, 2016, Duffy delivered one of the most memorable performances of his career, striking out 16 batters in a game against the Tampa Bay Rays, setting a Royals franchise record for strikeouts in a single game.

Duffy's tenure with the Royals was not without its challenges. Injuries continued to affect his availability, and his performance fluctuated at times. Nevertheless, he remained a respected figure within the organization and among fans. Off the field, Duffy was known for his community involvement and charitable efforts, further endearing him to the Kansas City community.

As the 2021 season unfolded, Duffy found himself dealing with more injuries, which limited his appearances on the mound. In July 2021, the Royals traded him to the Los Angeles Dodgers, although he did not pitch for them due to ongoing health issues. Despite the trade, Duffy's legacy with the Royals remained intact, as he had been a part of one of the most successful eras in the franchise's history.