Basel - Stan Wawrinka dug deep to defeat Donald Young 7-6 (7/4), 6-7 (3/7), 6-4 to return to the quarter-finals of the Swiss Indoors for the first time in five years.
The top seed in the absence of Roger Federer and Rafael Nadal was put through the wringer over three sets by American qualifier Young, with the Swiss emerging the winner thanks to 16 aces.
"It was not an easy match," the US Open champion said. "It took three sets, he was playing tough.
"I had to play well to go through. There was a lot of tension out there, especially in the third set. I'd call this a positive win for me.
"My goal now is only as far as the next round, I'll try to keep my level up in the quarter-finals. I hope to continue to play well."
Marin Cilic and David Goffin seemed headed in opposite directions in the race for the ATP World Tour Finals as Cilic earned a win while his rival took a loss.
Fourth seed Cilic reached the quarter-finals with a 6-0, 7-6 (7/4) defeat of Pablo Carreno Busta.
However, Argentine dangerman Juan Martin del Potro handed Goffin a 7-5, 6-3 defeat.
With two places remaining in the eight-man field for the November season wrap-up in London, Goffin stands on provisional ninth, with Cilic one spot behind.
But the Croatian, who will lead his nation in the Davis Cup final against Del Potro's Argentina later this year, is making up ground in the narrow points race.
Goffin has one chance remaining at next week's Paris Masters, the final event of the ATP regular season, where Cilic will also be playing.
Del Potro has risen 1,0000 ranking places this season since his February comeback from the latest in a series of wrist injuries which forced him to consider retirement.
He is making Basel his last tournament of the season as he prepares for the Davis Cup final.
Del Potro beat Roger Federer in the 2012 and 2013 finals in Basel.
The Argentine is looking forward to his quarter-final with Kei Nishikori.
"We last played at the London Olympics, but we are now different players. His game has improved a lot. He's one of the favourites to win the title here.
"I'm hoping to enjoy the match as it could be my last one before the Davis Cup final. I believe in my game, If I serve like I did today, I have my chances to win."
After defeating Carreno Busta, winner of the Moscow title last week, Cilic will next face a second Spaniard in Marcel Granollers, a 6-3, 6-1 winner over eighth seed Jack Sock.
Cilic won the last six points of his match against Carreno Busta after trailing 0-4 in the second-set tiebreaker. He delivered nine aces and 21 winners in a tie lasting just under 90 minutes.
In another second-round contest, Gilles Muller of Luxembourg beat Germany's Florian Mayer 6-3, 6-2.
Results on the fourth day of the Swiss ATP Indoors on Thursday (x denotes seeded player):
Stan Wawrinka (SUI x1) bt Donald Young (USA) 7-6 (7/4), 6-7 (3/7), 6-4
Marin Cilic (CRO x4) bt Pablo Carreno Busta (ESP) 6-0, 7-6 (7/4)
Marcel Granollers (ESP) bt Jack Sock (USA x8) 6-3, 6-1
Gilles Muller (LUX) bt Florian Mayer (GER) 6-3, 6-2
Juan Martin del Potro (ARG) bt David Goffin (BEL x5) 7-5, 6-3