Two-time French Open finalist Casper Ruud said the ATP's ranking system was like a "rat race" as players felt compelled to compete in the tour's mandatory events even if they are carrying injuries.

Seventh seed Ruud crashed out of the French Open on Wednesday after losing to unseeded Nuno Borges in the second round, with the Norwegian saying he had been struggling with knee pain that restricted his movement.

Asked if the busy tennis calendar made it difficult to take time off and fully heal an injury, the 26-year-old said players' rankings would take a hit if they skipped mandatory events.

"Well, it's kind of like a rat race when it comes to the rankings, as well," he said.

"You feel you're obligated to play with certain rules that the ATP have set up with the mandatory events.

"You feel like you lose a lot if you don't show up and play... the punishments are quite hard, in terms of everyone else will play, gain points, and you won't."

Ruud also said a player's year-end bonus was cut by 25 percent if they missed a mandatory event.

"I'm not sure if you're aware, but if you don't play a mandatory event, they cut 25 percent of your year-end bonus," he said.

"You're kind of forcing players to show up injured or sick, or whatever, when that is not what I think is very fair."

Ruud said he was looking forward to taking some weeks off to heal his injury before returning to the circuit.

"I'm just looking forward to not being on painkillers for some days now," he said.

"Let it really heal and rest and see where I'm at in a few weeks." (Reuters)