Write a question about the following article: Agassi opened 2001 by successfully defending his Australian Open title with a straight-sets final win over Arnaud Clement. En route, he beat a cramping Rafter in five sets in front of a sell-out crowd in what turned out to be the Aussies last Australian Open. At Wimbledon, they met again in the semifinals, where Agassi lost another close match to Rafter, 86 in the fifth set. In the quarterfinals at the US Open, Agassi lost a 3-hour, 33 minute epic match with Sampras, 76, 67, 67, 67, with no breaks of serve during the 52-game match. Despite the setback, Agassi finished 2001 ranked No. 3, becoming the only male tennis player to finish a year ranked in the top 3 in three different decades (1980s, 1990s, 2000s). He also was the oldest player (age 31) to finish in the top three since 32-year-old Connors finished at No. 2 in 1984.

Question about the article:
What all major tournaments did Agassi participate in in 2001?