Ronnie O'Sullivan registered the 995th century of his career but was made to work hard to beat Barry Hawkins 6-4 at the Players Championship.
The defending champion looked in ominous nick with a 106 clearance to take the first frame, and looked on course for another until running out of position having already wrapped up the second.
O'Sullivan's 51 break was enough to take the third but after a lengthy debate with the referee having been snookered, appeared to lose his rhythm.
Hawkins pounced with a century to cut the deficit heading into the mid-session interval, returning to take the following frame with a break of 55.
After O'Sullivan restored his two-frame cushion, Hawkins produced breaks of 65 and 110 to get within one yet again, but The Rocket found the answers to wrap up a 6-4 win with a break of 64.
O'Sullivan, who afterwards performed the post-match interview in an Australian accent, will now face Mark Selby or John Higgins in the quarter-finals.
On the other table, Mark Allen was dominant in a 6-2 victory over Stephen Maguire.
The Northern Irishman wasn't perhaps at his absolute best, but he didn't need to be, taking the first five frames with a high break of 67 before Maguire's 63 stopped the rot.
Maguire then produced arguably the break of the match to steal the seventh frame, firing in a nerveless 77 clearance having trailed 68-0 to keep hopes of a comeback alive.
Allen, at last finding real fluency against one of his closest friends on the circuit, responded with a frame- and match-winning run of 66 to progress to a clash with either a back-to-form Stuart Bingham, or German Masters finalist David Gilbert.
Monday's last 16 results
- Ronnie O'Sullivan 6-4 Barry Hawkins
- Mark Allen 6-2 Stephen Maguire
Tuesday's last 16 matches
- Neil Robertson v Joe Perry (1300 GMT)
- Mark Williams v Ali Carter (1300)
- Kyren Wilson v Jack Lisowski (1900)
- Judd Trump v Jimmy Robertson (1900)
Players Championship draw bracket
- Mark Allen v Stephen Maguire
- David Gilbert v Stuart Bingham
- Ronnie O'Sullivan v Barry Hawkins
- Mark Selby v John Higgins
- Neil Robertson v Joe Perry
- Mark Williams v Ali Carter
- Kyren Wilson v Jack Lisowski
- Judd Trump v Jimmy Robertson
