The Kansas City Royals drafted Simontacchi in 1996 out of San Jose State University. He joined the Capitals in 1998, where he dominated for one year. Following his 1998 season, the Pittsburgh Pirates purchased his contract. Simontacchi ultimately made his way to the St. Louis Cardinals in 2002. He was a part of the 2004 St. Louis Cardinals, who won the National League Championship, and went to the World Series. He finished his MLB career with a 26-17 record, an ERA of 5.09 and struck out 191 batters.
Most recently, Jason Simontacchi has been named the Royals Pitching Coordinator, after serving as the Assistant Pitching Coordinator from 2018-19.