[Kansas City.com] The Chiefs found their starting quarterback today by reaching an agreement to trade for San Francisco 49ers veteran Alex Smith, a source familiar with the deal told The Star.

The trade, first reported by Fox Sports, would indicate the Chiefs plan to part ways with Matt Cassel, who had been their starting quarterback most of the past four seasons.

In exchange for Smith, the Chiefs will give up their second-round draft pick in this April’s NFL Draft, No. 34 overall, plus a future conditional draft pick to the 49ers.

The trade will not become official until March 12, when the NFL’s new business year begins.

Smith sustained a concussion Nov. 11 and back-up Colin Kaepernick played well in his place. Coach Jim Harbaugh stuck with him even when Smith got healthy, and Kaepernick led the 49ers to the NFC championship and a close loss to Baltimore in the Super Bowl.

The 28-year-old Smith struggled for most of his career in San Francisco, plagued as much by coaching and coordinator changes as by his own indecisiveness. But when Harbaugh became coach, Smith blossomed. He was among the league leaders in passer rating (104.1) with a 70.2 completion percentage when he was injured in a 24-24 tie against St. Louis.