Murray struggled to hold serve in the early stages against Moya
Britain's Andy Murray battled back to beat Carlos Moya 2-6 6-3 6-1 and reach the Cincinnati Masters semi-finals.
The world number nine struggled to reproduce the form that saw him cruise past Dmitry Tursunov in the last round.
He was broken in the first game of the first set and was in big trouble when he dropped serve early in the second.
But he won five straight games to level the match and easily took the deciding set, booking a semi-final clash with Croatia's Ivo Karlovic.
Murray - so impressive in previous rounds in Ohio - failed to find any rhythm during the first set, struggling for first serves and consistently finding the net with returns.
He was broken three times as Moya - who had played two matches on Thursday - looked in complete control with his forehand dictating play.
I think I can win a Masters Series, and I'd love to do it this week
"It was really tough at the start," admitted Murray. "He was serving well, and I threw in a lot of unforced errors."
But the turning point came in the third game of the second set when Murray clawed back two break points to go 2-1 down.
The hold sparked an impressive resurgence as Murray's first serve suddenly began to fire, while Moya's rock-solid forehand deserted him.
Former world number one Moya stemmed the flow to hold at 4-1 in the third, but Murray secured the final two games to set up a last-four clash against Karlovic, who beat Germany's Philipp Kohlschreiber 7-6 7-6.
Big-serving Karlovic is in fine form after defeating world number one Roger Federer earlier in the tournament, but Murray is not intimidated by his 6ft 10in opponent.
"I think I can win a Masters Series, and I'd love to do it this week," said Murray. "I played well last week and had a tight match against Nadal.
"I'm playing well enough and can hopefully come through."
French Open and Wimbledon champion Rafael Nadal beat Ecuador's Nicolas Lapentti 7-6 6-1 and will play third seed Novak Djokovic who beat Latvia's Ernests Gulbis 6-3 6-4 in Friday's other quarter-final.