Philip Rivers is a top 8 QB in the NFL (I have him 6th) however he does have his share of weaknesses.
The biggest weakness our QB1 has is his poor pocket presence. Pocket presence is the ability to feel the pressure and make the appropriate move (usually to climb pocket or side step a rusher) while keeping eyes focused downfield on your receivers. The best QB in this area is the New England PatriotsTom Brady who seems to have eyes in the back of his head to see rushers and step up confidently and make throw.
A great example of bad pocket presence is Mike Vick who would see or feel a guy come free and would tuck it and run. At NC State Philip had some success doing just this. At this level he flat-out has no success and when he makes that fateful decision it usually results in a sack or a fumble.
Although there has been some improvement in this area since his rookie year, Philip still has struggled with feeling the pressure. Often times Rivers will see Jeromey Clary struggling with his man and choose to either throw the ball away, leave the pocket, or force a bad throw (something he did more often last year then in year's prior). He also begins to lose focus and instead of going through his progressions Rivers is focused on when Clary's man will come free. I usually refer to this as feeling "phantom" pressure as the pressure has not yet materialized and in some cases never will materialize, it is just a distraction that keeps 17 from making the right play. Another result of Phil feeling phantom pressure are his dump off passes to RBs or FBs out of the backfield usually ending in minimal gains.
Additionally Rivers has problems feeling pressure from the backside often times resulting in fumbles (9 in 2011, 7 in 2010, 6 in 2009, 8 in 2008, 11 in 2007, 8 in 2006 his first season as starter). Rivers doesn't see the LT lose his man and the ball is knocked away from him when the rusher hits him from behind.
The best solution to this problem is to have an offensive line that can protect your QB, however that wont be the case in Oakland this week and even if Gaither is back in week 2, Clary is still the RT for the entire year. So how can Phillip overcome this?
Well if I was the coach I'd have Phil work on his step ups and have unblocked guys come at him from all angles. Unfortunately for all of us, I'm not the coach and so this problem will likely be undressed as it has been for his entire career.
This by no means, is to say that he is a bad QB, Phil has many more strengths than weaknesses, however given the injuries and overall lack of ability of our offensive line this issue may rear its ugly head numerous times this season.
By the way if you are wondering Phil has a plus arm to go with plus short and intermediate accuracy, his deep ball accuracy is a tick above average. Phil also has a very quick release which makes up for his second biggest weakness (low release point). Therefore Philip grades out as a very very good QB, but I wrote this article for a reason. If River has another subpar year and the Chargers finish below .500 this will be one of the biggest reasons why.