Oakland traded him to Kansas City in, along with Mike Wood, as part of a three-way trade that sent Carlos Beltrán to the Houston Astros, Octavio Dotel from the Astros to the Athletics, and John Buck from the Astros to the Royals. Although he had been one of the most highly regarded prospects in the Oakland organization, he became available when the Athletics were able to sign Eric Chavez to a long-term contract. Royals management did not expect Teahen to make the opening-day roster in ; however, after hitting.344 in spring training and after injuries sidelined potential third basemenChris Truby and Chris Clapinski, the Royals announced Teahen would be their regular third baseman for 2005, and he made his major-league debut on April 4, 2005. His first hit was a triple and he hit 4 homers in his last 17 games of 2005. Teahen hit.240 in his rookie season with KC. In, he hit.290 with 18 home runs and 69 RBIs. During July, he raised his performance level with 10 home runs and 35 RBIs during the 38 games ending August 2. He continued to hit well, but suffered an injury and had to have season-ending surgery on September 8. Going into the season, Teahen moved from third base to right field because of the arrival of young prospect Alex Gordon. His HR total dropped alarmingly to only 7 homers, after hitting 18 the year prior. During the season, he hit two inside-the-park home runs, bringing his total for 2008 to 14 HRs. While in Kansas City, Teahen was a spokesman and fundraiser for a program that gave children with physical or mental challenges the chance to play baseball. Since Teahen obtained dual Canadian-American citizenship in 2005, he was able to play for the Canadian team in the 2009 World Baseball Classic. In, he hit.271 with a career-high 34 doubles, 12 home runs and 50 RBI in 144 games with Kansas City. He made 99 starts at third base, 31 in right field and three at second.
Chicago White Sox
On November 5, 2009, Teahen was traded by the Royals to the Chicago White Sox in exchange for infielders Chris Getz and Josh Fields. He later received the 2009 Hutch Award for his efforts on and off the field. On December 8, Teahen and the White Sox agreed to a three-year, $14 million deal.
On July 27, 2011, Teahen was traded to the Toronto Blue Jays with Edwin Jackson for Jason Frasor and Zach Stewart. The Blue Jays designated him for assignment on January 9, 2012. He was released on January 17. In his one season with the Blue Jays, Teahen played in 27 games, mostly as a pinch hitter and defensive replacement, and hit.190 with 1 home run and 3 RBI.
2012–2013
Teahen signed a minor league contract with the Washington Nationals on February 6, 2012. Teahen spent the 2012 season with the Nationals Triple-A affiliate Syracuse Chiefs. According to the International League transactions page, Teahen declared free agency on November 2, 2012. On November 26, 2012, Teahen signed a minor league contract with the Arizona Diamondbacks. He started the 2013 season with the Reno Aces, but was released by the Diamondbacks at his request on May 20. The Texas Rangers signed Teahen to a minor league deal on May 23, 2013, and assigned him to the Triple-A Round Rock Express. He was released on June 3, 2013. On June 17, 2013 he signed a contract to play for the York Revolution in the Atlantic League of Professional Baseball. Teahen signed a minor-league contract with the San Francisco Giants on February 15, 2014. This contract did not include an invitation to major league spring training. He was released on March 19. On December 15, it was reported that Teahen had retired.
Mark married Lauren McClain on December 31, 2010. They have three children. They also have three dogs, Espy, Ribi, and Ricki B. Espy has an account on Twitter.
