The game of golf is always changing.
So are the results when it comes to the list of the PGA Tour's best money earners. While there's every reason to believe that Rory McIlroy, Tiger Woods, Phil Mickelson and Bubba Watson will be at or near the top once again this year, it may not work out that way.
Not only could one one or two of those golfers have a disappointing year due to a slump or injuries, the game is so competitive that a number of middle-tier golfers could move up and finish in the top 20 or better.
Here's a look at seven golfers who have a good chance to improve their rankings in the 2013 golf season.