 Complete the following phrase:  Prior to turning professional, Xu began playing in minor-ranking Asian Players Tour Championship from age 15, and his first appearance at a ranking event was in the wildcard round of the 2014 Shanghai Masters where he was whitewashed 5-0 by Ryan Day. He also made a wildcard appearance at the 2016 World Open where he defeated veteran James Wattana 5-3 or progress to the last 64, where he lost in the next round against Daniel Wells. He made a further appearance at the 