By Matt Hladik Three-time Stanley Cup champion Duncan Keith announced his retirement today after 17 NHL seasons. Keith debuted with the Chicago Blackhawks in 2005 and spent 16 seasons with the team before finishing his career with the Edmonton Oilers. A four-time All-Star, he won the Norris Trophy as the NHL’s best defenseman in 2010 and 2014 and was the Conn Smythe Trophy winner as the MVP of the playoffs during the Blackhawks’ 2015 Stanley Cup run. Led by Keith, Jonathan Toews and Patrick Kane, Chicago won the Cup in 2010, 2013 and 2015 and also made trips to the conference finals in 2009 an…