|FC Seoul||3-0||Kashima Antlers
|Al Sadd||1-0||Al Shabab
K-League champions Seoul swept aside Oswaldo Oliveira's Kashima, who fell in the first knockout phase yet again. Bang Seung-Hwan, Dejan Damjanovic and Ko Myong-Jin got the goals. Click here to read the full match report
The visitors spurned a few early chances before Suwon captain Choi Sung-Kuk missed the best chance of the opening stages when he pushed his shot wide of the far post.
Suwon duly went ahead on 23 minutes when Lee Yong-Rae delivered a cross which Korean international Yeom Di-Goon headed past Nagoya keeper Seigo Narazaki.
Marcus Tulio Tanaka and Joshua Kennedy were only recently back after injury and both had chances before the interval as they searched for an equaliser. However, a mix-up in the Nagoya defence 11 minutes into the second-half allowed winger Lee Sang-Ho to tap into an empty net to double his side's advantage.
Suwon were content to sit back and try to hit their opponents on the counter-attack in the closing stages with Lee Sang-Ho narrowly shooting over late on, as Bluewings exacted revenge for a 2-1 defeat to Grampus at this stage of the tournament two years ago.
Zob Ahan did the damage early on, with Mohammad Ghazi showing brilliant feet inside the box before firing in the opener. The Greens went 2-0 up after five minutes when a corner eluded Al Nassr keeper Abdullah Al-Anzi to find Castro who headed home at the back post.
Castro made it 3-0 on 63 minutes when under pressure from Al Nassr defender Jon McKain he fired in a shot from inside the box which was too good for Al-Anzi.
Al Nassr's Kuwaiti international Bader Al Mutwa pulled one back for the Saudi Arabians on 66 minutes when he coolly rounded Zob Ahan keeper Shahab Gordan after a clever lofted through-ball.
However, the hosts confirmed their passage into the quarter-finals in spectacular style when midfielder Shahin Kheiri fired a wonderful long-range effort into the top corner. Al Nassr's day went from bad to worse when captain Hussein Sulaimani was sent off late.
Defender Abdulla Obaid Koni scored the game's only goal on 12 minutes from an Al Sadd corner. Obaid Koni deflected the corner into the back of the net past Al Shabab keeper Waleed Abdullah with what appeared to be a mix of his arm and shoulder.
Al Shabab, semi-finalists in last season's ACL, went in search of an equaliser and had genuine opportunities in the second-half, with Brazilian defender Marcelo Tavares glancing a free-kick narrowly wide on 68 minutes.
The White Lions' Guinea striker Alhassane Keita was busy late on and he was involved when substitute Abdullah Al Astaa forced a one-handed save from Al Sadd goalkeeper Mohamed Saqr when offered too much space just outside the box.
Keita almost levelled matters deep into stoppage-time when a loose ball inside the box fell to him but Saqr got down low to his left to hold firm and seal Al Sadd's place in the final eight after failing to get past the group stage in 2010.