Joo won 11-5,11-7,11-7,11-4.
Ma Lin continued his slide by losing to Xu Xin in straight sets. Ma Long survived a huge onslaught by Chen Qi and won in extra points in the decider.
In the Quarter affected by the withdrawal of Wang Hao, Adrian Crisan of Romania made the most of it by beating Chen Weixing to advance to a rare semi-final at this level. He faces Joo, who will not let such an opportunity of reaching the finals slip by.