Roger Federer has not ruled out playing the clay season this spring - if his body and mind continue to perform at their current high level.
"The clay season is up in the air," the 20-time grand slam champion said of his chances on stepping onto the dirt.
"If I'm playing a lot during this part of the season, it would be hard to play a robust clay season,"
"It would be light (schedule) if I do play. We'll see how it goes."
In 2017 Federer won the Australian Open on a hard-court surface, skipped the clay season including the French Open, and then returned to win Wimbledon on grass.
The Swiss is in Rotterdam on the cusp of overtaking Rafael Nadal as world No.1.
Should the wild card top seed reach the semi-finals this week, he would replace the Spaniard at the top of the ATP list and become the oldest man to ever lead the rankings.
"I'm healthy and glad to be playing," Federer said. "I should be playing when I feel that way and not play when I don't feel at 100 per cent or don't feel ready to do it."
Federer may well have to get past his long-time colleague and fellow Swiss Stan Wawrinka in order to achieve his return ranking dream.
Should the seedings hold up at the Ahoy stadium, the 32-year-old Wawrinka would be Federer's opponent in the Friday quarter-finals.
"I would love to be in that position with anyone, but with Stan it would be like a Grand Slam final, a big-time match," said Federer, Rotterdam champion in 2005 and 2012.
"I'm hoping to get to No.1 and hoping to do it this week. You always want to do it the tough way, it's not easy to get there.
"The achievement would be quite incredible. It's exciting to see Stan in my section and it's great to have him back (after knee surgery in July)."
Federer bases his optimism on his solid, comprehensive performance last month in lifting a sixth Australian Open trophy as he defended a grand slam title for the first time in a decade.
"In Australia, I played it not thinking about No.1, which I thought was probably won't happen or is too far out of sight," he said.
"I didn't think of the rankings at all in Melbourne. Afterwards, I thought I could always play Rotterdam, I'd love to play, give it a go and see what happens.
"I'm happy I'm here, healthy and eager to play," he said before starting late Wednesday against Belgian Ruben Bemelmans.