The Associated Press

INDIANAPOLIS - Al Unser Jr. woke to a harsh reality this week: His passion for racing was gone.

On Wednesday, Unser announced his retirement, stepping away from a successful career.

"Racing has to come before everything else in your life," he said. "I've reached a point where helping my sons and daughters means more to me today than driving into Turn 1."

Unser, 42, leaves open-wheel racing as one of its most successful drivers. In more than 21 seasons, Unser won two Indianapolis 500s, two CART championships and a combined 34 races on the CART and Indy Racing League circuits.

He will serve as an adviser for Patrick Racing, his team, and a mentor for his 21-year-old son, Al, who will make his Infiniti Pro series debut this weekend. Team owner U.E. "Pat" Patrick has not named a replacement driver for Unser for this weekend's IRL race in Kansas City, Kan.

"You just know when it's time," Unser said at a news conference at Indianapolis Motor Speedway. "... I'm no longer willing to maintain that level of sacrifice or desire."

This season was especially frustrating for Unser.

He worked for several months to find a ride after breaking his pelvis in October when he was thrown from an all-terrain vehicle. After months of rehabilitation, Unser signed with Patrick Racing in March but missed the first three races of the IRL season.

In three starts, Unser's best finish was 11th, and last weekend at Richmond, he was the slowest qualifier. Unser finished 22nd in what turned out to be his final race. The next day, he decided to leave.

Unser always felt the pressure of his family's legacy. His father, Al Sr., is one of three drivers to win four Indy 500s. His uncle Bobby won the race three times.

The younger Unser won the closest-ever Indy 500, defeating Scott Goodyear by 0.043 seconds in 1992. His other Indy victory came in 1994 when he started from the pole.

"I've had a great career," Unser said. "It's been a challenge, been hard to follow in the footsteps I've followed. But I feel I upheld the Unser name quite well."