Safin has been slumping this year, playing his first semifinal this week in his first claycourt appearance of 2003.
The 2000 U.S. Open champion last competed for a title at the Paris Masters in November, winning the week before the Masters Cup in Shanghai.
"I won here three years ago, but a lot of things have changed," he said. "Now I'm the man to beat. I like my claycourt game now. I'm playing quickly and putting the pressure on my opponents. I need to keep motivated and aggressive."
Safin used a power game to his advantage against Ferrero, who won a week ago in Monte Carlo and was unbeaten in 10 straight matches -- including the Davis Cup -- on red dirt.
"Hard matches are what I need now, I need to build up my confidence again," Safin said. "Today certainly helped in that. I want to start winning tournaments and earning points again."
The Russian won the first set as Ferrero sliced short, then double-faulted. From then on, Safin grabbed the momentum, racing to 5-0 on an ace. His backhand down the line did much of the damage against the crowd favorite.
Safin let it slip just slightly as Ferrero saved a match point before the big Russian gathered his game again for the final dash to victory. He fired two aces in a row to end it after 70 minutes.
Ferrero heads south to his hometown of Valencia, determined to keep up his preparation for the French Open next month.
"I was serving well, I don't know how I made that double-fault," he said. "That mistake put me right out of the match. My momentum totally stopped and he continued to play great.
"I'm upset, but you can't win every time, that's tennis. It was a difficult match. I don't know why, but I wasn't on my best game. I wasn't tired physically or mentally, but that's tennis."