Adam Vinatieri walks the sidelines after missing a 29 yard field goal late in the fourth quarter

For the second game in a row this season, the Super Bowl champion  Colts lost.  It was a 23-21 loss Sunday as they battled the San Diego Chargers.  Darren Sproles returned the opening kickoff and a first-quarter punt for touchdowns as the Chargers raced out to a big lead and held on to beat the Colts at rainy Qualcomm Stadium.  LaDainian Tomlinson added a four-yard touchdown run in the second quarter for San Diego, which built a 23-0 lead and picked off Peyton Manning a career-high six times to hold on for the victory.  Adam Vinatieri missed a 29-yard field goal with 1:31 to play for Indianapolis, which lost its second straight after starting the season 7-and-0.  Manning finished 34-of-56 for 328 yards and two touchdowns and the six interceptions.  Reggie Wayne had an eight-yard TD reception late in the third quarter and Kenton Keith hauled in a seven-yard scoring pass early in the fourth.  Gary Brackett recovering a fumble in the end zone for a TD just 25 seconds later to get the Colts within two.  Philip Rivers was just 13-of-24 for 104 yards and two interceptions, but the Bolts still improved to an AFC West-leading 5-and-4.