CHICAGO -- Roger Federer is contemplating a significant change to his 2019 schedule.

Federer, who credited much of his resurgence since the start of 2017 in which he won three majors to a decision to avoid the entire European clay-court segment (including the French Open), might return to the red-dirt grind next season.

"The clay-court season is under review," Federer told ESPN.com at the Laver Cup, which begins Friday. "It's not off the table. I will know by the end of the year."

Avoiding the clay enabled Federer, 37, to save energy, train and adequately prepare his game for the grass-court season. Grass is the surface on which Federer's game is most effective, and Wimbledon begins less than a month after the end of the French Open.

Federer did not say how many clay events he might play, but he has three ATP Masters 1000 events to choose from, as well as a host of lesser events before the French Open begins.

"I would like to make up my mind ahead of time so I can plan my buildup, my fitness schedule, even the way I would approach my December practice sessions," Federer said. "It could benefit the clay-court season."

The No. 2-ranked Federer knows what he is up against. "This is something that is obviously a big deal. If you play the clay, it changes everything."

Federer played in five French Open finals, winning one in 2009, when he completed his career Grand Slam. All four of his finals losses were to Rafael Nadal, who is the defending champion at Roland Garros and still ranked No. 1 in the world.

Federer's ranking could be impacted by this decision. A good result would earn him clay points for the first time in two years. But should Federer struggle on the clay or find himself low on energy later in the year because he played on the clay, it could have a negative effect. So why would he return to clay?

"Just because I want to do it," Federer said. "It's a full-on passion thing."