1. Strength gap: Xu Xin, as the world champion of men's singles, needs to match female players with equal strength, while Sun Yingsha is outstanding in women's singles, but there is a big gap with Xu Xin.
2. Tactical considerations: Based on tactical considerations, tacit understanding among players, competitive situation and other factors, the coaching team decided not to choose Xu Xin and Sun Yingsha as partners.
3. Inexperience: Sun Yingsha, as a young player, may not be able to take the initiative to solve the problem like an experienced player in the face of competition difficulties, which may be the reason why Xu Xin is dissatisfied in the mixed doubles competition.