Nadal needs to win the Monte Carlo Masters for an 11th time in order to fend off Roger Federer at the pinnacle of the world rankings.
Novak Djokovic was knocked out of the Monte Carlo Masters by an inspired Dominic Thiem in the third round on Thursday, with the Austrian fifth seed progressing to a possible quarter-final with Rafael Nadal.
"It's a way better feeling if you go against him and know that you've beaten him already on this surface", Thiem said. "That excites me to get out on Saturday and play my match, simple as that".
Dimitrov was particularly tested at 4-0 down in the second set, when he won six of the final seven games-including the tiebreak-to send Nadal a message of intent and his pedigree in playing under pressure.
The Spanish veteran is challenging for a record 31st Masters title, 24 of which have been on clay.
He proved more stubborn as he saved two break points in the sixth game before surprisingly breaking back to give the world number 38 hope of taking the opener. It was the 12th time Nadal had whitewashed a set against a top-10 player, and he got the second set underway with another love hold.
Nadal continued: "I can't let him play from easy positions". While Nadal has reached the quarterfinals or better in Monte Carlo for 14 years in a row, Thiem is through to the quarterfinals of the tournament for the first time in his career.
There is tournaments that I can't imagine missing the tournament on objective, because is the tournaments that I love to play.
Heading to the semi-final clash, Nadal leads Thiem in their head-to-head by 5-2.
Third seed Alexander Zverev beat Jan-Lennard Struff 6-4, 4-6, 6-4, but missed out on facing his older brother Mischa Zverev in the last eight.
Goffin will play fourth seed Grigor Dimitrov for a place in the semi-finals in a repeat of last year's ATP Tour Finals final, after the Bulgarian came back from a set and a break down to beat Germany's Philipp Kohlschreiber 4-6, 6-3, 6-4. The ball, which was traveling slowly, bounced and clipped the ball boy on the head.