Andy Murray came through strongly at the end of two tight sets to beat Croat Marin Cilic 7-5 7-6 and progress to the quarter-finals of the Madrid Masters.
The Scot trailed for most of the first set but saved three set points at 4-5 and broke Cilic again to wrap it up.
The second set went with serve until Murray broke Cilic, the world number 24, to go 5-3 up, only to drop his own serve when aiming to finish the match.
Murray won the tie-break 7-2 and will play Gael Monfils in the last eight.
The Frenchman, who Murray has played twice before - winning one and losing one of their two encounters on clay in 2006 - overcame American Andy Roddick 6-4 3-6 6-3.
Murray confessed to becoming a little confused during his first full competitive match, after his second-round opponent Simone Bolelli retired, following a three-week break.
"I didn't know what the score was [in the second set]," he said.
"I didn't know I was serving for the set and I asked the umpire if that was actually the score - that hasn't happened to me on the tour before.
"Marin's a tough guy to play against because he hits the ball flat and has a big serve, so I just had to try and stay focused.
"When you trade groundstrokes with him he is very, very good but he started to make a few mistakes as the match went on."
The Scot took his time to get warmed up, a pair of double faults handing Cilic an early break at 2-1 and the Croat, heralded as a future top-10 player, kept Murray at bay with some rasping serves and fierce groundstrokes.
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The world number four broke back at 5-5 with a stunning backhand and, with Cilic's momentum brought to a grinding halt, Murray broke him again to wrap up the set.
Both players seemed shy about seizing the initiative in the second set and Murray waited patiently to pounce on Cilic's errors and break at 5-3, only for the Croat to break straight back.
But Murray raced away in a one-sided tie-break as Cilic's game deserted him, and Murray - despite appearing to struggle with a knee problem at one stage - moved into the last eight with some ease.
"It's sore today, the court is gritty and the ball was bouncing very low," he added.
"When that happens I bend down and do some cracks and it starts to ease off. At the beginning of the second set it felt a little bit better."
Rafael Nadal and Roger Federer edged closer to a title showdown after easily overcoming their opponents.
Nadal beat Richard Gasquet 6-4 6-2 and if he reaches the final on Sunday the Spaniard is guaranteed to end the year as world number one after displacing Federer in August.
Federer beat Frenchman Jo-Wilfried Tsonga 6-4 6-1 and will next play ninth seed Juan Martin del Potro, who enjoyed a 6-4 6-2 win over fellow Argentine and seventh seed David Nalbandian.
Victory for Federer took him past Pete Sampras to become the ATP tour's all-time leader in prize money with $43,317,870 (£25,020,402).
However, Federer insisted: "It's not very special. It's very nice to have records. Sure, money is important in life but it's not everything."
Ivo Karlovic produced an upset as he defeated Novak Djokovic 7-6 7-6, his aggressive game and ferocious serve provoking his opponent into fits of raquet throwing and shouting.
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