Defending champion Mark Selby was left with plenty to think about overnight following an enthralling first session of his Betfred World Championship semi-final with Ding Junhui.
There was little to split the pair in Sheffield on Thursday before Ding, who lost to Selby in last year's final, won the final three frames to secure a 5-3 advantage.
They shared the opening four frames of the best-of-33 clash at the Crucible, with Ding twice edging ahead.
The 30-year-old Chinese player cleared up with a break of 76 in the first and then took the third with a run of 84 after Selby had again let him back in.
Selby responded on both occasions, producing an audacious pot on a red on his way to a break of 68 in the second and then falling one point short of a century in the fourth.
The contest became a far more tactical affair following the mid-session interval and Selby edged in front for the first time at 3-2 following a frame lasting almost 34 minutes.
The world number one had cruised through to the last four, dropping only 11 frames in comfortable victories over Fergal O'Brien, Xiao Guodong and Marco Fu but, as expected, Ding was proving to be a far more formidable opponent.
He pegged back Selby after another lengthy frame of safety exchanges before runs of 56 and 50 in the seventh saw the world number four restore his lead.
Ding then ensured he would take a slender advantage into the second session by wrapping up the final frame with the first century of the match (110).
