Stan Wawrinka continues calls for stricter umpiring after French Open fourth-round win

Stan Wawrinka said the adjudicating of the 25-second rule in tennis needs to be more strictly adhered to.

Just days after French Open organisers adhered to a request from Rafael Nadal to not be umpired by Brazilian Carlos Bernardes at the clay-court major, Wawrinka continued to call for the rule to be monitored more closely - having slammed the Nadal-Bernardes decision after his second-round win.

Bernardes and Nadal have a controversial history, with the adjudicator coming down on the 14-time major winner for perceived time-wasting strategies - most recently in Rio de Janeiro in February.

Wawrinka, this time, was speaking after earning a quarter-final berth at Roland Garros, having dismissed 12th seed Gilles Simon 6-1 6-4 6-2.

"I think the ATP [World] Tour had to change, to be more strict was the 25-second rule, but I don't think it's really working well, because the umpires... they're not really consistent with that," Wawrinka said.

"Maybe you can put the clock, like in basketball.

"You can always try, it can be something to try, but it's not easy to find what would be the good thing for the game.

"In tennis, you can't push the player to play, and only have 10 seconds between points."

Wawrinka has matched his equal-best effort in Paris by reaching the last eight, which he previously did in 2013.

While he readily admits his game is more suited to hard courts, Wawrinka said his experience on the surface earlier in his career has stayed with him.

"I think maybe I play my best game on a good, outdoor hard court," the 30-year-old said.

"The feeling to come back onto the clay is always easy, always nice, always natural to change surface, as I know I did last year for the Davis Cup.

"I can change in two days and feel really good already on the clay, because I grew up on the clay.

"I was playing until 20 years old, I was playing almost only clay-court tournaments, Challenger [Tour] and satellites before.

"So that was the reason why I was feeling better on clay at the beginning.

"But when you play on the Tour, you play way more on hard courts, so you need to improve your game on hard court, and that's what I did."