Valerio De Los Santos, a left-handed pitcher from the Dominican Republic, embarked on his Major League Baseball journey when he was signed by the Milwaukee Brewers. His debut came on June 7, 1998, marking the beginning of a career that would see him play for several teams over the next decade. Known for his fastball, De Los Santos quickly became a reliable option out of the bullpen for the Brewers.

During his tenure with Milwaukee, De Los Santos showcased his ability to handle pressure situations, often being called upon in late innings. His time with the Brewers lasted until 2002, after which he was traded to the Philadelphia Phillies. Although his stint with the Phillies was brief, he continued to demonstrate his pitching skills, contributing to the team's bullpen depth.

In 2003, De Los Santos joined the Toronto Blue Jays, where he continued to pitch in relief. His role remained consistent, providing innings and stability to the bullpen. The following year, he signed with the Florida Marlins, further extending his career in the majors. With the Marlins, De Los Santos continued to be a part of the bullpen rotation, offering his experience and left-handed pitching to the team.

After his time with the Marlins, De Los Santos had a brief period with the Colorado Rockies in 2005. Although his appearances were limited, he maintained his presence in the league, showcasing his ability to adapt to different teams and situations. Following his stint with the Rockies, he spent some time in the minor leagues and independent baseball, continuing to pursue his career in professional baseball.

In 2008, De Los Santos made a return to the majors with the New York Mets. His time with the Mets was short-lived, but it marked the end of his journey in Major League Baseball. Throughout his career, De Los Santos was known for his left-handed pitching and his ability to contribute to various teams' bullpens. His career spanned multiple teams and leagues, reflecting the journeyman nature of many professional athletes.