After having seen Shen Lian dodge the fist, Emperor Xia retracted his Primordial Spirit and returned to normal size. A coldness flashed through his eyes, and his flesh and body pierced through the air. He chased after Shen Lian and left behind only a stream of air.
When Shen Lian dodged Emperor Xia's attack, the latter could feel that the former's divine Qi had gaps that could be taken advantage of. With his discerning eye, he would surely not miss such an opportunity that comes only once in a blue moon.
In the end, Shen Lian's state of Primordial Spirit, as well as the light travel speed, was more nimble and quick as compared to when he initially performed it with his mortal body. If Emperor Xia did not firmly lock his spiritual senses, Shen Lian might not catch up with him even if the duration of the technique used by the emperor was less than ten minutes.