Mar 29, 2017; Miami, FL, USA; Kei Nishikori of Japan holds a towel over his head during a changeover against Fabio Fognini of Italy (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Fognini won 6-4, 6-2. Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Kei Nishikori of Japan reaches for a backhand against Fabio Fognini of Italy (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Fognini won 6-4, 6-2. Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Fabio Fognini of Italy reaches for a forehand against Kei Nishikori of Japan (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Fognini won 6-4, 6-2. Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Fabio Fognini of Italy serves against Kei Nishikori of Japan (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Fognini won 6-4, 6-2. Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Kei Nishikori of Japan hits a forehand against Fabio Fognini of Italy (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Fognini won 6-4, 6-2. Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Fabio Fognini of Italy hits a forehand against Kei Nishikori of Japan (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Fognini won 6-4, 6-2. Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Rafael Nadal of Spain hits a backhand against Jack Sock of the United States (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Jack Sock of the United States reaches for a forehand against Rafael Nadal of Spain (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Rafael Nadal of Spain celebrates after his match against Jack Sock of the United States (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports0
Mar 29, 2017; Miami, FL, USA; Rafael Nadal of Spain hits a forehand against Jack Sock of the United States (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Jack Sock of the United States hits a backhand against Rafael Nadal of Spain (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Rafael Nadal of Spain reaches for a forehand against Jack Sock of the United States (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Rafael Nadal of Spain (R) shakes hands with Jack Sock of the United States (L) after their match on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Jack Sock of the United States hits a forehand against Rafael Nadal of Spain (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Rafael Nadal of Spain hits a forehand against Jack Sock of the United States (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Rafael Nadal of Spain serves against Jack Sock of the United States (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Jack Sock of the United States hits a forehand against Rafael Nadal of Spain (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 29, 2017; Miami, FL, USA; Rafael Nadal of Spain hits a volley against Jack Sock of the United States (not pictured) on day nine of the 2017 Miami Open at Crandon Park Tennis Center. Nadal won 6-2, 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Rafa Nadal moved into the Miami Open semi-finals with a straight sets win over American Jack Sock on Wednesday, while second seed Kei Nishikori was sent packing after going down 6-4 6-2 to unseeded Italian Fabio Fognini.
Nadal staved off four break points to avoid going down a double-break early in the second set, a pivotal game that set the stage for his 6-2 6-3 victory on the Crandon Park hardcourt.
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Nadal's poise and shotmaking came to the fore when 13th seed Sock threatened to take a stranglehold on the second set.
“That was the key of the second set, two-love (down), 15-40,” Nadal said in a courtside interview. “With three-zero a player like Jack, you’ll probably be thinking third set.
“It was a double positive thing. I saved that game and got the break back (in the next game). The match was much closer than the result says.”
Nadal could face his long-time nemesis Federer in the final, with the Swiss, who has a Thursday quarter-final against Tomas Berdych, on the other side of the draw.
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Federer and Nadal have met twice this year, with Federer winning both times, in a memorable five-set final at the Australian Open and in a one-sided straight-sets fourth-round thumping at Indian Wells two weeks ago.
But Nadal is not looking ahead to Federer, because his semi-final opponent Fognini presents a potential banana skin. Nadal has a 7-3 career record but is mindful he lost to the Italian in a five-set thriller on the U.S. Open hardcourt in 2015.
"It’s like a dream maybe,” said the 29-year-old Fognini after becoming the first unseeded player in 10 years to make the Miami semis.
“This is a big, big tournament for me. I’m happy about my performance. I’m just trying to be focussed on my game and do my best.”
(Reporting by Andrew Both in Cary, North Carolina; Editing by Greg Stutchbury/Peter Rutherford)