By KC Joyner The biggest question in the San Diego-Indianapolis matchup this weekend is how the Chargers' secondary will hold up against the Colts' passing game. San Diego ranks 27th in passing yards allowed per game, 24th in opponent's passer rating, 25th in interceptions and 22nd in completion percentage. Everything about those statistics seems to indicate the Colts will have an easy time. However, that might not be the case. San Diego has played five games against teams ranked in the top nine in passing yards per game (Kansas City, New England, Oakland twice and Philadelphia). The Chargers went 4-1 in those games, and they likely would have been 5-0 if not for the blocked field goal that was returned for a touchdown at the end of the Philadelphia game. San Diego did not win these games in shootouts. It allowed an average of only 16 points per game, and the highest point total it allowed in any of these games was 20. I conducted an analysis of these five games and found that the Chargers have a scheme that actually can be quite effective against vertical passing teams. One of the problems the San Diego secondary had in 2004 was that it couldn't play man or zone coverage very well. The unit played poorly in man coverage because its talent level was average. The Chargers were also very young on defense, with a new scheme, so they struggled with the proper zone coverage coordination. They are doing a much better job in zone coverage in 2005. San Diego's cornerbacks frequently are playing at least seven yards off the line of scrimmage at the snap (and sometimes more) to get into the deep zone more quickly, and its linebackers are getting into the short zones effectively. The Chargers used primarily this effective zone coverage against the five opponents listed above, and it is the reason they were able to put up the following metrics in those games (the yards per attempt include penalty yards). Passing Test Depth Att Comp Yds TDs INTs Pen Yds/Att Short 136 98 727 1 0 -5 5.4 Medium 47 26 403 3 2 -5 8.7 Deep 26 9 264 1 3 0 10.2 Totals 209 133 1394 5 5 -10 6.7 These numbers are fairly good. The short, deep and total yards per attempt stats would correspond to a top-10 ranking over the course of a season, and the medium numbers are solid. San Diego's cornerback depth is part of the reason its opponents' short pass completion percentage is so high (72 percent). It's also why the Chargers are doing as well as they are against these teams in deep passing. If San Diego has done so well in these games, why are its overall rankings so poor? There are two reasons. The first is the number of potential interceptions the defense has dropped. In these five games alone, the Chargers dropped nine potential interceptions. They did intercept five passes, but it could have been much better. The primary reason is that their cornerbacks still aren't very good individually in coverage. Take the Miami game from this past weekend as an example. Here are the Chargers' route depth metrics from that game: Cutting Corners Depth Att Comp Yds TDs INTs Pen Yds/Att Short 15 9 81 0 0 -5 5.7 Medium 3 2 23 1 2 0 7.7 Deep 5 3 125 1 0 0 25.0 Totals 23 14 229 2 2 -5 10.2 The short and medium numbers are quite good, but the deep numbers obviously tell the story. Quentin Jammer and Drayton Florence were beaten on deep passes in this game. Jammer was beaten on a triple move route (hook/out/go) by Marty Booker for a 56-yard completion. He also almost was beaten for a 25-yard TD on a post route by Booker in the third quarter, but Jammer reached out and hit the ball just as it arrived to force the incompletion. Florence was beaten on a post route to Chris Chambers for a 35-yard TD. On another play, it looked as though Florence blew a coverage on a corner route to Chambers for a 34-yard completion.