I've seen Philip Rivers play several times, and everytime I see him, I think I am watching Bernie Kosar play again.
The similarities between the two are astonishing. Both are tall drop back passers. Rivers stands around 6-5, 230 lbs. Kosar was 6-5, around 225 lbs. Both have side arm release points. Both are very accurate passers. Both are typically mistake free quarterbacks.
When Bernie played for the Browns, that guy was one of the most accurate passers in the NFL, and he was known for his ability to avoid interceptions and avoid taking sacks. Back then, Marino and Kosar were always the least sacked quarterbacks in the NFL, and a lot of that had to do with how quickly they got rid of the ball.
Dan's throwing mechanics weren't the best there were either. He threw the ball from a higher angle than Kosar and Rivers do, but he wasn't a true overhand passer. A lot of quarterbacks throw the ball from a release point above their head. Marino's was from the ear. Kosar and Rivers throw it from a point below the ear.