Paris ? On her last day as a teenager, Kim Clijsters took yet another French Open letdown like a grown-up.

Two years ago, Clijsters lost the longest third set in a women’s final at Roland Garros, and Saturday she lost the most lopsided final in 15 years. But she greeted Justine Henin-Hardenne at the net with a warm smile after her Belgian compatriot won the title, 6-0, 6-4.

“I wasn’t even close to playing my best tennis today,” the No. 2-seeded Clijsters said. “But I’m happy for Justine that she won.”

They’ve been friendly rivals for so long that Clijsters can’t remember the first time they played each other — possibly in a 10-and-under event. She had won seven of their 12 matches as pros but was no match for Henin-Hardenne in the first all-Belgian Grand Slam final.

Clijsters, who turns 20 today, was less patient and less consistent than Henin-Hardenne. Clijsters didn’t move as well, and when she became frustrated that Henin-Hardenne was getting so many balls back, she tried for too much and sprayed her shots.

The four games Clijsters won were the fewest for a French Open finalist since Steffi Graf beat Natasha Zvereva 6-0, 6-0 in 1988.

She said jitters were not the problem.

“I was nervous a little more than normal, but not that it was influencing me on my tennis,” Clijsters said. “In this tournament I haven’t played my best tennis, but I still went through to the finals, which is a good sign.”