David Newhan's journey in Major League Baseball began when he was drafted by the Oakland Athletics in the 17th round of the 1995 MLB Draft. He made his MLB debut with the San Diego Padres on April 27, 1999. During his time with the Padres, Newhan played as an infielder and outfielder, showcasing his ability to adapt to different positions on the field.

After his stint with the Padres, Newhan spent some time in the minor leagues before being picked up by the Philadelphia Phillies in 2000. His tenure with the Phillies was brief, and he continued to move between teams, seeking opportunities to establish himself in the major leagues. In 2001, Newhan signed with the Texas Rangers, where he played a handful of games before returning to the minors.

A turning point in Newhan's career came in 2004 when he joined the Baltimore Orioles. This period marked his most productive years in the majors. Newhan's performance with the Orioles was highlighted by a memorable game on July 21, 2004, against the Boston Red Sox, where he hit for the cycle, becoming the first Oriole to do so since 1999. His ability to deliver in clutch situations and his versatility on the field earned him a more regular spot in the Orioles' lineup.

Newhan's time with the Orioles lasted until 2006, after which he signed with the New York Mets in 2007. With the Mets, he continued to play as a utility player, filling in various roles as needed. His experience and adaptability made him a valuable asset to the team, even though his batting average fluctuated during this period.

In 2008, Newhan signed a minor league contract with the Houston Astros and was called up to the majors later that year. He played in a limited capacity, primarily serving as a backup and pinch hitter. Despite not being a regular starter, Newhan's presence in the clubhouse and his readiness to step in when called upon were appreciated by his teammates and coaches.

Throughout his MLB career, Newhan was known for his work ethic and ability to play multiple positions. His journey through various teams and leagues exemplified the challenges faced by many professional athletes striving to maintain a place in the competitive world of Major League Baseball. After retiring as a player, Newhan transitioned into coaching, sharing his knowledge and experience with the next generation of players.