Lee Chong Wei
The world number one from Malaysia was never in difficulties in a 21-17, 21-19 win over Tienh Min Nguyen, the seventh-seeded Vietnamese player, but reckoned his performance fell below his usual very high standards.
There were some moments of exceptional brilliance from Lee, sometimes with agile defence, sometimes with airborne attack, and twice with spectacularly dismissive brushed kills at the net.
However he appeared oddly distracted at others, notably when he let slip four match points in a row, before concluding a superb attack-defence-attack combination on the fifth with a flying jump smash.
“I made some simple mistakes,” he said, shaking his head. “I just have to forget about it and move on. I must do that because no next opponent will be dangerous.”
He will also be unusual. Tanongsak Saensomboonsuk is a qualifier who has worked his way diligently all the way to the semi-finals, scattering some notable opponents along the way.
He squeezed past the sixth-seeded Chinese player Hu Jun in a thriller, then outplayed Sho Sasaki, the top 20 Japanese player, and now proved consistently too good for Tommy Sugiarto, the son of former world champion Icuk Sugiarto, winning 21-17, 21-11.
Despite the emergence of theThai surprise packet, it is Chen Long who appears to be the biggest threat to Lee, with his great movement and control, and increasing patience and maturity.
Chen won a match full of deft rallies with mesmerising patterns against Kashyap Parupalli, the top ten Indian, who led 13-11 but could make no further headway.
Chen was denied the expected semi-final with his compatriot Chen Jin however, when the former world champion was well beaten 21-7, 21-14 by Jan Jorgensen.
The unseeded Jorgensen had never previously been beyond the second round but was admirably quick and assertive, though he appeared to benefit for the second match in a row from an opponent  with less than adequate fitness.
Yesterday, the fourth seeded Sony Dwo Kuncoro retired against him with a bad back; now Chen Jin’s movement was so laboured that he lost 15 of the first 18 points and was hardly in contention. At the end the Dane placed his hand on the Chinese player’s arm by way of consolation.
Although it is good for the tournament to have a European in the men’s singles semi-finals he may find Chen Long, the winner of the World Super Series finals in Shenzhen in December, a rather different proposition.
Chen Long gives that impression too. “I played really well,” he said. “I feel pretty good about how I am playing in the tournament so far.”