Mayer, seeded second, defeated Italy's Filippo Volandri in the other semifinal 7-6 (3), 6-2.
Chela beat Andujar in last year's final. This time, the fourth-seeded Spaniard made an excellent comeback in the first set after trailing 4-1.
Chela broke to lead 3-2 in the second set and the match looked headed for a third set, with the Argentine serving at 5-4. But Andujar broke and then held to lead 6-5, winning on his third match point.
In the other semifinal, Volandri broke Mayer to go up 5-3 in the first set, but the German immediately came back with a break of his own before serving out for 5-5. In the tiebreaker, Mayer took a 5-1 lead, helped by two aces and a double-fault by Volandri before wrapping up the set with another ace.
The Italian made a strong start in the second set, breaking serve to lead 1-0. But Mayer rallied again, before accelerating to a comfortable victory.