At the time of the battle and shortly thereafter, many people thought that if the overall commander was Bai Chongxi or Li Zongren instead of Chen Cheng, than China could have won.
Ultimately, all that is needed is that China is able to inflict enough casualties that Japan realizes taking the city won't lead to the collapse of the Chinese war effort and that a stalemate would be the result regardless if the city was taken. If so, they could disengage in order to conserve their forces and begin their long war strategy of blockade.
I think there are several PODs that could have generated that. On the drive up the Yangtze to Wuhan, several Chinese river forts were seized quite easily because of various stupid things its commanders did. Prevent those, and the Japanese take longer time to get to Wuhan and have more casualties. A different strategy at Shanghai could do the same. If Han Fuqu fought at Jinan and delayed the Japanese from crossing the Yellow River, or if there was a follow up at China's victory at Taierzhuhuang.
Earlier PODs that accelerated the Nationalists control of China or their industrial development would also help since they'd allow for more weapons, organization, or preparations.