But his fast lap of 1 minute, 21.434 seconds -- 102.208 mph (164.488 kph) -- 11 minutes from the end of qualifying buried Alesi's day-old record of 1:23.519 on the newly configured course, revised since last year due to construction.
"The lap itself was great," Senna said. "It was not a matter of sliding around, just the measure between aggressive driving and good performance under control. You have to be very precise and very clear on your perceptions."
Alesi crashed during a hot lap late in the final session and was unable to improve on his first-day lap, falling to sixth on the 26-car grid for today's 82-lap race.
Prost, whose Ferrari was third after Friday's time trials, jumped to the top 19 minutes into yesterday's 60-minute session with a lap of 1:23.204 on the 2.312-mile (3.720-kilometer) circuit.
Senna, the defending race and series champion, one-upped his bitter rival and former teammate one minute later, lowering the fast time to 1:22.831.
Prost, who won the inaugural Phoenix race in 1989, returned the compliment at the 40-minute mark with a sizzling 1:22.555, but Senna's all-out final effort on his second and last set of qualifying tires nine minutes later overwhelmed his rival and the rest of the competition.
"I was highly motivated," said Senna, whose Friday effort was inhibited by a minor problem with the McLaren team's new 12-cylinder Honda engine. "We lost [the top spot] yesterday and I wanted to recover it.
"Yesterday, we did everything right and calculated to go out right at the end [of the session] and had a very small problem with the engine. . . . A very small thing ruined it."
Senna said he concentrated on the race setup in yesterday's morning practice period and had to use the first of his two allowable sets of qualifying tires to get the car just right for his record run.
"The first [qualifying run yesterday] was a good one, but not maximum. I used the experience of the first to run the second."
1. Ayrton Senna, Brazil, McLaren Honda, 1 minute, 21.434
seconds, 102.208 mph; 2. Alain Prost, France, Ferrari, 1:22.555; 3. Riccardo Patrese, Italy, Williams Renault, 1:22.833; 4. Nigel Mansell, Britain, Williams Renault, 1:23.218; 5. Nelson Piquet, Brazil, Benetton Ford, 1:23.384; 6. Jean Alesi, France, Ferrari, 1:23.519; 7. Gerhard Berger, Austria, McLaren Honda, 1:23.742; 8. Roberto Moreno, Brazil, Benetton Ford, 1:23.881; 9. Emanuele Pirro, Italy, Dallara-Judd, 1:24.792; 10. J.J. Lehto, Finland, Dallara-Judd, 1:24.891.
11. Stefano Modena, Italy, Tyrrell Honda, 1:25.065; 12. Martin Brundle, Britain, Brabham-Yamaha, 1:25.385; 13. Mika Hakkinen, Finland, Lotus-Judd, 1:25.448; 14. Bertrand Gachot, Belgium, Jordan Ford, 1:25.701; 15. Pierluigi Martini, Italy, Minardi-Ferrari, 1:25.715; 16. Satoru Nakajima, Japan, Tyrrell Honda, 1:25.752; 17. Nicola Larini, France, Lamborghini, 1:25.791; 18. Ivan Capelli, Italy, Leyton House Ilmor, 1:26.121; 19. Eric Bernard, France, Lola Ford, 1:26.425; 20. Thierry Boutsen, Belgium, Ligier Lamborghini, 21. Aguri Suzuki, Japan, Lola Ford, 1:26.548; 22. Gabriele Tarquini, Italy, AGS Ford, 1:26.851; 23. Mauricio Gugelmin, Brazil, Leyton House Ilmor, 1:26.865; 24. Mark Blundell, Britain, Brabham-Yamaha, 1:26.915; 25. Michele Alboreto, Italy, Footwork-Porsche, 1:27.015; 26. Gianni Morbidelli Italy, Minardi-Ferrari, 1:27.042.
Failed to qualify Eric Comas, France, Ligier Lamborghini, 1:27.159; Alex Caffi, Italy, Footwork Porsche, 1:27.519; Stephan Johansson, Sweden, AGS Ford, 1:27.753; Julian Bailey, Britain, Lotus-Judd, 1:28.570.
NASCAR Busch 200
MARTINSVILLE, Va. -- Things may be changing on the NASCAR Grand National circuit, and today's Busch 500 could be the beginning of that change.
Elton Sawyer is on the pole for the race, and his hopes of winning his first race on the circuit are riding on Hoosier tires, not Goodyear.
Sawyer, whose team serves as the prime testers of the new bias-ply racing tires, is one of four drivers in the top six who qualified Hoosiers. Dave Rezendes qualified second, Butch Miller fourth and Joe Nemechek sixth.
Hoosier, which last supplied tires to Winston Cup and Grand National in 1989 and carried Darrell Waltrip to his Daytona 500 win that year, has renewed its battle with Goodyear on the Grand National circuit.
"We feel the Hoosiers are the only viable product for these kinds of race cars," said Bob Newton, president of the Lakeville, Ind., company.