Debby Day was named the head coach of Cal Lutheran softball in the summer of 2002.

In 2015 she guided the Regals to their first 20-win season since 2009 and their first ever SCIAC Postseason Tournament since its inception in 2008. Day led CLU to its best conference finish since 2009 and helped deisgnated hitter Blake Lewis earn NFCA All-West Region honors and First Team All-SCIAC.

In 2008 and 2009, catcher Emily Robertson earned NFCA All-West Region under Day. Then in 2019 and '18, third baseman Kendall Marinesi was named NFCA All-West Region First and Third Team, respecitvely. 

Following the 2005 season, third baseman Prudence Kjontvedt was named to the Louisville Slugger/NFCA All-America First Team and earned SCIAC Player of the Year honors. She hit .547, the second highest batting average in the nation.

In 2003, the Regals posted the best season in the history of the school since joining the NCAA. They finished 24-20, won the league title, and advanced to the NCAA West Regionals in Spokane, Washington. CLU won two games against Chapman and dropped two against Pacific Lutheran in the northwest. It was the fifth SCIAC championship the Regals had won.

Day brings extensive experience on both the playing and coaching sides to Cal Lutheran. She has been the head coach of the Burbank High School varsity softball team since 1997. Prior to that, Day was an assistant coach at NCAA Division I member Iowa State from 1993-95. She also works with Mike Candrea's Southwest Softball Camps.

As a two-year player at the University of Arizona, Day, primarily a pitcher and first baseman, was a member of the 1991 national championship team. The 1992 team won the Pac-10 championship and was a runner-up at the World Series. Day was tabbed all-American, all-World Series and All-Pac-10 both seasons. 

Before joining the Wildcats, Day played two seasons at the University of Texas-Arlington (1988-89). In 1988, Day led the nation in season strikeouts and broke seven Southland Conference records, including most wins, innings pitched, strikeouts and lowest ERA.

Day received a degree in American Literature with a minor in Communications from Arizona in 1992. 

Day has a daughter, Kylie.