Gary Anderson was the last back-to-back winner of PDC World Championship in 2015 and 2016
Former winner Rob Cross cruised through at the PDC World Championship and set up a last-16 tie against defending champion Luke Littler.
Cross, who won the event in 2018, brushed aside Australian and 16th seed Damon Heta in a comfortable 4-0 win.
The 17th seed was joined in round four by two-time winner Gary Anderson, who edged a final-set thriller against Dutchman Jermaine Wattimena.
Scot Anderson went 3-1 up in a game played at a ferocious pace, and was impressive in averaging 121 in set three.
