DAYTONA BEACH, Fla. -- Dale Earnhardt Jr. and Elliott Sadler won the two 125-mile qualifying races to set the stage for Sunday's Daytona 500.

It's a one-of-a-kind event because it's the only race on the Nextel Cup circuit where drivers have qualifying races to get into Sunday's race.

The racers who finished in the top 15 of each race were guaranteed a starting spot in the Daytona 500. Greg Biffle and Sadler locked in the first two starting spots with the fastest laps in last Sunday's pole qualifying. Earnhardt will start in third place, and Sterling Marlin's final lap pass of Kevin Harvick in the second qualifying race means he will start in the fourth position.

Sadler beat Marlin to the checkered flag by 0.669 seconds. It was Sadler's first career Gatorade 125 win.

Jimmie Johnson, Mark Martin and Kevin Harvick completed the top five.

The importance of doing well in Thursday's 125 races is highlighted by the fact that 69 of 90 (73.6 percent) winners at Daytona have started in the top 10.

Qualifying times from last Sunday were used to set the lineups for Thursday's two qualifying races. Odd numbers -- first, third, fifth and so on -- went into the first race, even numbered qualifiers competed in the second event.

Results from the qualifying races set positions three through 30 for Sunday's "Great American Race."

In the opening qualifying race, Earnhardt beat Tony Stewart by 0.245 seconds.

The Daytona 500 is set for Sunday.