Kansas City Chiefs quarterback Alex Smith agreed to a four-year contract extension reportedly worth around $68 million.  The move allows Kansas City to use the franchise tag next season on linebacker Justin Houston, ESPN reports.

Smith, entering the final year of his contract, signed an extension on Sunday.  The Kansas City Star first reported the news, and the Chiefs later confirmed the signing on the team website.

"It was a priority of ours to get this deal done and keep Alex in a Chiefs uniform long-term," general manager John Dorsey said in a statement, released via the team website.  "Alex is a proven leader on and off the field.  He is a special individual with a lot of ability, and we are fortunate to have him here."

Chiefs coach Andy Reid added: "Alex is a smart, talented football player that has adapted well to our offensive scheme.  He also, obviously, has had a tremendous amount of success as a quarterback in this league.  We as a team are very happy to have Alex as our quarterback moving forward."

Kansas City acquired Smith in a trade with the San Francisco 49ers in March 2013.  The deal cost the Chiefs two second round picks - in 2013 and 2014 - but brought stability under center.  Smith quietly threw for a career-best 3,313 yards and 23 touchdowns last season with the Chiefs, helping the team to an 11-5 record and their first playoff berth since 2010.

Locking up Smith for through the 2018 season will likely lead to Kansas City using the franchise tag on Houston after the season, according to ESPN.