Twenty-time Grand Slam champion Roger Federer has criticised Italian Open organisers for doubling ticket prices after it was confirmed he would play.
Federer, 37, is playing the clay-court season for the first time since 2016.
The number three seed, who has a first-round bye and will begin his tournament against Portugal’s Joao Sousa, said the decision was “disappointing”.
“They made it in a way like they rewarded the fans who bought tickets earlier, which is sort of strange.”
Federer added: “I just really hope it doesn’t take away the fact I’m really happy to be here. There’s going to be good crowds hopefully, good atmosphere.”
Thiem saved two match points to beat Federer and progress to the Madrid Open semi-finals last week, but Federer was pleased by a strong performance and has his eyes on a second French Open title in June.
His only Roland-Garros title came a decade ago when he beat Swede Robin Soderling in straight sets.
“I think I was playing well in Madrid, so I just said, again, ‘let’s come to Rome, a city I like so much as well’,” said Federer.
“Madrid is a tough place to play. I felt like playing maybe more sea-level conditions would be good for me. There would be excitement, more excitement than me coming to a practice court in Switzerland.
“Regardless of what happens here, I just think it’s good for me to play matches at this stage.”