Belgian world number one Justine Henin believes compatriot Kim Clijsters has chosen the right time to retire.
Clijsters and Henin played their first match as seniors in 1998
Clijsters, 23, who grew up with Henin through the juniors, planned to quit at the end of the season but announced her immediate retirement on Sunday.
"When I heard Kim planned to play only certain tournaments, I thought she would find it hard, because you have to be 100% focused," said Henin.
"So it was a surprise, but she has made the right decision to bow out now."
It was a good story for Belgian tennis, because we were so different
Clijsters decided to bring her decision to retire forward, saying "the fire had died out", and Henin, who held a 12-10 record over Clijsters, said she would definitely be missed on the tour.
"Belgian and world tennis is losing a great champion for sure," said Henin.
"We virtually grew up together and played a lot of tournaments together, we have lots of respect for each other, but we were rivals.
"It was a good story for Belgian tennis, because we were so different in our styles.
"We should never forget what Kim Clijsters has done for tennis. I wish her all the best for her new life after tennis, it is going to be a big change for sure."
Clijsters, who won 34 career titles, plans to marry Belgium-based American basketball player Brian Lynch in July.
Henin is continuing her build-up to the defence of her French Open title at the German Open in Berlin and faces German wildcard Tatjana Malek on Wednesday.
On the second day of the event, ninth seed Anna Chakvetadze needed three sets to see off Australian Samantha Stosur 3-6 7-6 (7-1) 7-6 (7-5).
Fellow Russian Elena Dementieva also went the distance against Italian Mara Santangelo, eventually winning 4-6 6-1 6-4.
Germany's Martina Muller topped Eleni Daniilidou of Greece 6-0 6-2 while China's Yan Zi defeated German Kristina Barrois 4-6 6-3 6-2 to line up a second-round match against second seed Amelie Mauresmo.