PARIS -- Add US Open champion Dominic Thiem and the man he beat at the French Open on Friday, No. 28 seed Casper Ruud, to the growing chorus of players who think electronic line-calling should come to clay-court tennis.
It's not a new idea. And there are questions about the accuracy of that sort of system on clay, where the red dust shifts, making it harder for the machine to be as right as it can be on hard courts.
Still, just in the past couple of days at Roland Garros, top-10 seeds Stefanos Tsitsipas and Denis Shapovalov have raised the issue, as did 2018 semifinalist Marco Ceccinato, who grumbled about it during the third set of his third-round loss Friday.
"Today in my match there was a mistake -- in my favor actually," two-time French Open runner-up Thiem said after beating Ruud 6-4, 6-3, 6-1. "Casper showed me the mark on his phone after the match."
Thiem played at a tournament in Brazil where a system fine-tuned for use on clay was tested.
"There were not any issues," he said. "So I hope that next year, we will have it in every clay-court tournament."
After Ruud disputed a couple of calls with the chair umpire, some buddies back home in Norway who were watching the match took a picture of one of the ball marks on the TV screen and sent it to his phone.
"It was quite clearly out," he said.