Cassel has completed 1,042 of 1,767 passes for 11,699 yards with 76 touchdowns and 45 interceptions for an 82.5 passer rating. He has also rushed 193 times for 711 yards (3.7 avg.) with three scores. He originally entered the NFL as a seventh-round pick (230th overall) of New England in the 2005 NFL Draft from the University of Southern California.
Horne (6-2, 193) has played in six games with Kansas City. Horne originally joined the club as a rookie free agent from the University of Massachusetts in 2010.
Earlier this month, Chiefs coach Todd Haley didn't rule out the possibility of placing Cassel on injured reserve.
"He will probably have to have surgery at some time," Haley told reporters. "The length of it, we're not sure, but there's some optimism. Each person it varies, but it's a difficult injury. This has been a fluid situation"
Cassel got hurt during the Chiefs' loss to the Denver Broncos when he got sacked by Elvis Dumervil.
Without Cassel, the Chiefs have gone with Tyler Palko as their starting quarterback.
Palko, who has also played for the New Orleans Saints after playing collegiately at Pitt, has only played in four NFL games.
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Matt Cassel placed on IR
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