Mark Selby with a shock 3–5 defeat to Andrew Pagett in the qualifying rounds of the 2013 Wuxi Classic. The tournament was the first to use a new format that required top-16 players to compete in qualifiers. In minor-ranking tournaments, Selby was runner-up in the Yixing Open, where he lost 1–4 to Joe Perry, and the Rotterdam Open, where he lost 3–4 to Mark Williams. He won the Antwerp Open, defeating Ronnie O'Sullivan 4–3 in the final. In December, in the seventh frame of his UK Championship semi-final against Ricky Walden, Selby compiled snooker's 100th officially recognised maximum break in professional competition.
Mark Selby He continued his form at the Shanghai Masters, where he won his second major ranking event by defeating Mark Williams 10–9 in the final, having trailed 9–7. The win also meant Selby usurped Williams as the world number one, making him the ninth player to hold the top spot and the first to do so without having previously won the World Championship. He also won the minor-ranking PTC Event 4 (also known as the Paul Hunter Classic) with a 4–0 whitewash over Mark Davis, having edged out Ronnie O'Sullivan 4–3 in the semi-finals. Selby would later finish 5th on the