"The interest that I was getting wasn't significant enough for me to go through the grind of another year and be away from my family," Westbrook told Rob Rains of stlsportspage.com. "I was kind of 50-50 on whether I wanted to play anyway. I'm good with the decision."
Westbrook was the No. 21 overall pick by the Rockies in the 1996 First-Year Player Draft and appeared in three games with the Yankees in 2000 before being traded to the Indians. He spent nine years in Cleveland before being dealt to St. Louis during the 2010 season.
Westbrook was 105-103 with a 4.32 ERA in 315 games (273 starts).
Westbrook, who has four children -- Parker (8), Keaton (6), Harper (3) and Paxton (16 months) -- said he's ready for the next chapter.
"I'm excited about the next part of my life, and that's being home with the kids and my wife, Heather, and spending time with them and going to all of the things I haven't had a chance to do over the last 18 years in the spring and summertime," Westbrook told stlsportspage.com. "Being home is going to be fun."
Cash Kruth is a reporter for MLB.com. Follow him on Twitter at @cashkruth. This story was not subject to the approval of Major League Baseball or its clubs.