O'Sullivan edged into the lead twice in the morning, but two magnificent century breaks levelled things up for Robertson, who finished the session 5-4 up.
However, he found himself facing even bigger problems when his cue-tip disintegrated in the sixth frame - but played on regardless.

'That's hurtful!' - Robertson takes lump out of cue tip

Shanghai Masters
O'Sullivan lifts Shanghai title for third successive year
15/09/2019 AT 14:24
O'Sullivan was resurgent in the evening, though, rolling through four frames in succession to give himself a 9-5 advantage.
The Australian stayed in touch but O'Sullivan was not to be denied, wrapping it up 10-6 to secure his place in the final against Shaun Murphy on Sunday.

O'Sullivan downs Robertson to reach final

Shanghai Masters
O’Sullivan wins third consecutive Shanghai Masters
15/09/2019 AT 09:06
Shanghai Masters
O'Sullivan knocks in second ton against Murphy
15/09/2019 AT 14:14