So far 2012 has been remarkable season in tennis for many reasons.
After Andy Murray won his first major at the 2012 U.S. Open, it meant that each of the top four men in tennis had won a Grand Slam title.
Roger Federer regained the No. 1 ranking after a long absence from the top, reinforcing the notion that age 30 is not a death sentence in tennis.
But probably what stands out most so far in 2012 are the number of breakthrough performers populating professional tennis.
A few players, rooted in place a long time, finally broke through to the upper echelons of the game while some relative newcomers had an occasion to showcase their potential and significantly advance in the rankings.
The breakthrough performances took players to levels they had never before achieved.
They are all the 2012 most-improved players to watch from now until the end of year as the tour turns the corner and heads toward 2013.