Former world number one Marcelo Rios returned to competitive action for the first time in two years with victory over Thomas Muster on Wednesday.
Marcelo Rios reached number one in the world in 1998
The Chilean, who retired from the ATP Tour in July 2004, made his debut on the Tour of Champions in Doha.
And Rios impressed with a 6-3 6-1 win over 1995 French Open champion Muster.
"I thought I was going to feel a little bit worse, but I've been practicing for the last month so I'm feeling pretty good," said Rios.
He added: "In the beginning, after my retirement, I said I'm not going back (to tennis) again.
"I was tired of travelling and practicing. Now, after two years, I've decided to play on the Merrill Lynch Tour of Champions and see how it goes.
"I'll try to enjoy it and play a bit more relaxed, but I also think when you have been at the top you still like to win. Everybody that comes here wants to win the title.
"I'm just enjoying playing again, taking it match by match. If I can win, that would be great.
"It's exciting to be back and I'm looking forward to playing good and just enjoying tennis for a second time."