The Belgian was all aggression as he beat Stefano Galvani, while the Spaniard was all calm and precision against Kevin Kim on way to the last 8 of the Chennai Open.
The Indo-Belgian pair lost 4-6, 4-6 to Leos Friedl and Mikhail Youzhny in the men's doubles first round.
Agassi, who has not seen action since a third-round loss to Rafael Nadal at Wimbledon, is seeking a fifth title in Los Angeles.
Roddick will be hoping to win his first trophy since Lyon last October. He holds a 6-1 record over Blake, his poker-playing partner.
The third seeded pair lost their semi-final match against unseeded Belgian pair of Xavier Malisse and Oliver Rochus.
Thomas Johansson rattled off a whirlwind 6-2, 6-1 win over Stefan Koubek in the first round of the Barcelona Open
Lleyton Hewitt breezed into the last four of the Tennis Channel Open with a 6-2, 6-0 win over Philip Kohlschrieber
Clijsters and Xavier Malisse gave Belgium a 2-0 winning lead over Slovakia in the Hopman Cup.
The third seeded pair registered a comfortable 6-3, 6-4 win against Karsten Braasch of Germany and Sargis Sargsian of Armenia.
The Belgian world number 36 was banned for "aggravated behaviour" after being kicked out of the Nasdaq-100 tournament.
Xavier Malisse took his second Delray Beach title by beating American James Blake 5-7, 6-4, 6-4.
Belgian Xavier Malisse won the first ATP title of his career as he upset Jiri Novak 7-6 6-2 in the final of the Millennium International Tennis Championships at Delray Beach on Sunday.
Joachim Johansson and Thomas Enqvist both won second-round matches in the Australian men's hardcourt championship.
The top seeded American could meet his former housemate, Nicolas Thomann, in the title round at the RCA championships
The 33-year-old's win over Xavier Malisse in the Stella Artois Championships vaulted him to the top.
The women's top seed won at love against Barbara Schett while Agassi beat Xavier Malisse at the French Open.
The top seed powered into the semi-finals of the Los Angeles Open with a 6-2, 4-6, 6-4 win over Paradorn Srichaphan.
The top seed will face Kenneth Carlsen in the semi-finals after the unseeded Dane beat American Jan-Michael Gambill at the Kroger St Jude ATP event.