Coming back from a blowout win against Tennessee, the Texans went to face an undefeated Chiefs team. However, tragedy struck when DE J. J. Watt  suffered a season ending leg injury in the first quarter that was later revealed to be a tribal plateau fracture to his left leg.   OLB Whitney Mercilus also suffered a season ending  pectoral injury.   Taking advantage of the Watt injury, the Chiefs jumped out to a 16-0 lead 26 minutes into the game. Houston came within 6 points of the lead early in the fourth quarter, but the Texans defense could not keep up with the Chiefs offense. The Chiefs won by 8 points and the Texans fell to 2-3 on the season. Watt and Mercilus ended up having a major impact on the team, the team going 2-10 without them (including the Chiefs game) and 2-2 with them.. Who suffered a season ending leg injury in the game?