It showed too when he came back to the table three frames behind and missed a simple red to allow Trump back in.
Fate presented the Northern Irish player with an opportunity though, Trump undone by a massive kick to allow Allen to make 56 and get on the board.
Shots Recreated: Ronnie and Jimmy attempt Trump's tasty double
He then flew out of the mid-session interval with a masterful break of 140 and followed it up with 106 to level the match and confirm that this final would live up to its billing.
He made it 4-3 a few minutes later with Trump, conceding the frame with only one snooker required, clearly rattled as he left the arena momentarily.
Whatever he did with his break seemed to work, even if he needed the table to level the kick count when Allen had 35 on the board and a 5-3 lead in his sights.
Judd Trump produces total clearance to cut the arrears
Instead, Trump pulled back level and there was one more stroke of luck that turned the match again. After the two men had exchanged breaks of 40 and a safety battle, Trump attempted a long red that rattled the left corner pocket, and flew directly along the cushion in to the right. He needed no second invitation.
The world champion sunk a long red in the 10th frame and then went into the pack with perfection, sealing the a place in the semi-final as the clock approached 10pm with a break of 98.
He will now take on Neil Robertson in a final which Allen himself admitted 'should be a cracker'.