Andy Murray became the first British player to make the last four of Italy's premier tournament since 1932 after beating Florian Mayer 1-6 6-1 6-1.
Unorthodox world number 28 Mayer dominated the first set with some inspired play as the Briton struggled.
But Murray eventually took control of an intriguing match, proving too savvy for a player he had never met before.
Fourth seed Murray will face Novak Djokovic, who beat Robin Soderling 6-3 6-0, in Saturday's semi-final.
In reaching the last four, Scotland's world number four - who is targeting his first Masters title on clay - won his 100th Masters match just two days before he turns 24.
He did so by digging into his well of inner belief against a player whose thrilling purple patch in the early stages of the match had Murray troubled initially.
"I definitely thought well on the court, which is something I wasn't really doing in the States in March," he told BBC Sport.
"I was happy with the way I managed to turn it around. He was a tricky opponent who made it tough for me, but I played well in the end. I started the match off pretty uptight, wasn't really that sure of myself and was a bit negative.
"But I got myself together and finished it off. My attitude's been better [recently]."
Murray, first to serve, started the rot himself by ceding the early initiative with a number of forehand errors.
A simple smash crashing into the net then gave the 28-year-old German a chance to break, which he aggressively pounced on before rapidly taking his own first service game.
The Scot then stylishly won his following service game to love, but Mayer simply stepped up to dominate the rest of the set.
Murray did earn a break-back point with a good push return on second serve in the following game, but Mayer saved well before executing a brilliant drop shot which allowed him to draw Murray in before lobbing him perfectly to take a 3-1 lead.
Inventive Mayer then earned himself a break point with a superb blocked return down the line on his backhand and once again he held his nerve, with Murray clearly rattled by the German's use of an unpredictable choppy double-handed backhand.
After saving two break points, Mayer closed out his next service game before breaking shell-shocked Murray - who only recorded a 50% first-serve percentage in the first set - with shots that included a scorching cross-court return and another brilliantly-weighted lob to close out the 32-minute first set.
But Murray dug deep to send out an immediate message with an instant second-set break after Mayer hit a cross-court backhand too long in a marathon rally.
The Scot allowed himself to be broken back in the next game after Mayer's stunning slice up the line, but it only concentrated his mind further as he battled on doggedly for another break.
Now in a groove that enabled him to pick up more forehand winners, Murray clinched an important hold before a surge of points meant he won the rest of the set as Mayer's mind clearly turned to the decider.
Serving, Murray eventually took a sixth game in a row in the first game of the third set by utilising his heavy forehand well.
His momentum was unstoppable as he broke Mayer once again with the technical elements of his play clicking into place superbly, before holding once more with relative ease.
Mayer - who has reached six quarter-finals or better on the tour so far this year - did manage to snatch his first game in nine, but calm Murray stayed in control to close out the match with a confidence that bodes well for tougher challenges ahead.
"It's a tough tournament with loads of history, all the best players come here as it's great preparation for Paris," said Murray. "I've been hitting the ball well and come through some tough matches.
"It would be great to end Novak's unbeaten run, if I play him. I feel confident and I think I can beat him. I feel fresh and I'm looking forward to it [the semi-final]."
The last British man to reach the semi-finals at this event was George Hughes who, a year earlier in 1931, became the only British man to win the tournament.
"When we walk to the practice court they have a list of all of the winners down the wall, and there is a lot of great players," added Murray. "It is nice and I want to try and go further."