Hoping to rebound from their home loss to the Broncos, the Chargers flew to Arrowhead Stadium, donned their throwbacks, and played a Week 7 AFL Legacy game with the Kansas City Chiefs.  In the first quarter, San Diego struck first with quarterback Philip Rivers competing a 3-yard touchdown pass to wide receiver Malcom Floyd and a 10-yard touchdown pass to wide receiver Vincent Jackson.  The Chargers would continue their dominance in the second quarter as kicker Nate Kaeding nailed a 20-yard and a 39-yard field goal. The Chiefs would get on the board in the third quarter with quarterback Matt Cassel completing a 7-yard touchdown pass to wide receiver Dwayne Bowe, yet San Diego came right back with Rivers hooking up with running back Darren Sproles on a 58-yard touchdown pass.  Afterwards, the Chargers would wrap up the game in the fourth quarter with Kaeding booting a 19-yard field goal and fullback Jacob Hester recovering a blocked punt in the end zone for a touchdown.. How many touchdown passes did Rivers throw in the first quarter?