Complex sentence: After the UK Championship, Higgins slipped to number 12 in the world rankings, having failed to reach the quarter-finals of any tournament since the Wuxi Classic in June.
Split into simpler sentences: After the UK Championship, Higgins slipped to number 12 in the world rankings. By the year's end, he had failed to reach the quarter-finals of any tournament since the Wuxi Classic in June.