Roger Federer moved to within three wins of his 100th career title on Wednesday after beating Fernando Verdasco 6-3, 3-6, 6-3 to move into the Dubai Championship quarter-finals.
Twenty-time Grand Slam winner Federer said he was "living on the edge" after a hard-fought last 16 victory at the Aviation Club which handed him his 50th win at the tournament.
The 37-year-old is now the tournament's highest seed following s 7-5, 5-7, 6-2 defeat at the hands of unfancied young gun Hubert Hurkacz earlier on Wednesday.
Nothing came easy on the night for Federer, whose victory was a near-duplicate of his rugged opening round win over Philipp Kohlschreiber on Monday.
"You're definitely living on the edge at some point in the match. This is how it is," Federer said afterwards.
"I'm happy I stayed calm throughout, I was having a good feeling out there, even though I wasn't playing my best.
"I still felt like it was going to fall my way when it really mattered."
Nishikori's shock defeat to 22-year-old Hurkacz has made Federer's job this week slightly easier, but the Swiss wasn't publicly confident of making the career century after another tough win.
"I'm not sure if I'm going to get to 100. Let's put it that way," added Federer, who will play Marton Fucsovics after the Hungarian's 6-4, 6-2 win over Jan-Lennard Struff.
Hurkacz, ranked 77th in the world, moved into his first ATP quarter-final after needing just over two hours to complete the upset over Nishikori on a windy court, his first top 10 scalp.
"It's a huge win for me because it's the first top 10 win," Hurkacz said. "It gives me huge confidence. I'm going to try to keep going forward."
The Japanese top seed was at a loss to explain exactly what went wrong in the first-time meeting with the Pole.
"I didn't play perfect today, but I think he was playing good serves, better than I thought," Nishikori said.
"With this wind and this surface, it's not easy. I didn't serve well when I wanted to.
"He played well in the important games, I didn't make many first serves when I wanted to... that cost me some important points."
In the quarter-finals, Hurkacz will take on fifth seed Stefanos Tsitsipas, who cruised to a straight sets win over Egor Gerasimov 6-3, 6-1.
"Everything was going up to my game plan. I didn't feel any pressure -- less pressure today than the other day," Tsitsipas said.
"I didn't feel stress, that's why I played so free and so relaxed, was always motivated. Even when I was a break up, I always wanted more and more."
France's Gael Monfils crushed Marcos Baghdatis 6-3, 6-2 in 65 minutes.
Following up on his upset of third seed Marin Cilic the day before, Monfils dominated former Australian Open finalist Baghdatis.
The 32-year-old will play Ricardas Berankis, a winner over Denis Kudla 6-4, 6-1, on Thursday for a place in the semi-finals.For all the latest business news from the UAE and Gulf countries, follow us on Twitter and Linkedin, like us on Facebook and subscribe to our YouTube page, which is updated daily.
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