The Associated Press captures the performance well:
Tiger Woods arrived at Augusta National as a favorite to win his fifth green jacket. Instead, he left with his worst score as a pro.
This chart, made with data from the Augusta Chronicle, shows his four-round average scores at the Masters since he turned pro in 1997. This year was the highest (which, in golf, if a bad thing):
It should be noted that weather conditions vary each year. Tiger finished second in 2007 when low temperatures and wind made scoring difficult, for example. Still, it’s a general indicator of performance. Another measure is the leader board position: Tiger finished 41st this year, by far his worst effort.