He will be 30 years old when the season starts, will make $5.1 million this season, only one 1,000 yard season during his 8 year career, and a team was willing to offer up a 2nd round choice for him. THAT is why Chambers was traded.
Chambers was fun to watch, and he is very talented. He could make the most acrobatic catch, but at the same time he would drop the easiest of passes. Plus when he would drop those passes, he would always flip his wrist looking for the invisible flag(which was annoying). He will never be a huge star in the league, but on an explosive offense like the Chargers, he will have some success.
In a league where Pro Bowl record breaking receivers go for 4th round picks, you have to take a second round pick for a second tier receiver like Chambers.