Teenager Sinner beats Rublev to reach Barcelona last four
Sinner, ranked 19th in the world, will face the winner of Stefanos Tsitsipas and Felix Auger-Aliassime's quarter-final later in the day.
"I am trying to get better every week,"Sinner said.
"He (Rublev) has played many, many matches already this year and I tried to play my tennis.
"It was difficult to finish it off. I had three break points at 5-5 (in the second set), which I could not convert, but I'm pleased to win in the end," he added.
Rafael Nadal, who has won 20 Grand Slam single titles, reached the Barcelona last four as an 18-year-old 16 years ago.
Later Nadal faces Britain's Cameron Norrie for a place in the semis as he seeks a 12th title in Barcelona.