Federer was stretched to three sets for the second day in a row in the Chinese capital after overcoming Roberto Bautista Agut of Spain – 6-3, 2-6, 6-4.
Just 24 hours earlier, Federer was pushed all the way in his victory over Russia’s Daniil Medvedev.
And Federer’s reward for coming through a tough battle is a quarter-final meeting with Kei Nishikori.
The Swiss legend admits he wants to wrap things up a lot quicker this time.
He said: “As we know with Kei’s game, once he finds his range and his rhythm, he’s very tough to play.
“I think it’s going to be a tough match tomorrow. I hope it’s going to help me that I played against [Daniil] Medvedev and also Bautista Agut, two really good baseliners, to be honest.
“From that standpoint, I feel like I found a rhythm. Now it’s just up to me to play a good match myself.
“I need to focus a lot on my serve to make sure I can always keep the upper hand there.”
Conversely, Del Potro – who has been suffering with a cold throughout the week – retired at the end of the first set against Borna Coric which he lost 7-5.
As things stand, Federer could meet Coric in the last four providing he gets past Nishikori.
With Del Potro, who has booked his place at the World Tour Finals at London’s 02 Arena, will be hoping to make amends at the last Masters 1000 series in Paris next month.
The Argentine – who is currently ranked fourth in the world – insists he’s not too fussed about the battle with Novak Djokovic and Federer for the number two spot.
“I’m not thinking about the rankings much,” Del Potro said.
“I had my highest ranking ever this season.
“There’s a lot of motivation to fight with the top guys for the first positions.
“I’m glad with my number and the top guys deserve to be there.
“It’s more interesting for the fans as to whether I get there.”
Conversely, Del Potro – who has been suffering with a cold throughout the week – retired at the end of the first set against Borna Coric which he lost 7-5.
As things stand, Federer could meet Coric in the last four providing he gets past Nishikori.
With Del Potro, who has booked his place at the World Tour Finals at London’s 02 Arena, will be hoping to make amends at the last Masters 1000 series in Paris next month.
The Argentine – who is currently ranked fourth in the world – insists he’s not too fussed about the battle with Novak Djokovic and Federer for the number two spot.
“I’m not thinking about the rankings much,” Del Potro said.
“I had my highest ranking ever this season.
“There’s a lot of motivation to fight with the top guys for the first positions.
“I’m glad with my number and the top guys deserve to be there.
“It’s more interesting for the fans as to whether I get there.”