After slipping to a 13-7 defeat to the 'The Jester from Leicester' in the last eight at the Crucible Theatre on Tuesday morning, Robertson found little of the match a laughing matter.
But he also paid tribute to the “unbelievable” safety tactics of his hardened opponent, who claimed world crowns in Sheffield in 2014, 2016 and 2017.
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Selby has been installed as the new 14/5 favourite for a fourth triumph as he prepares for a semi-final over the best of 33 frames against Mark Williams or Ronnie O'Sullivan.
He survived a last-frame decider in a 13-12 win over Noppon Saengkham in the last 16, but was much more dominant against Robertson.
Selby said "I had got so used to winning tournaments that when I wasn't winning tournaments it became very damaging to my confidence. I was happy with my performance against Neil. I felt if I got a chance I could score, and my safety play was back up with how it was a few years ago.
"As a matchplay game it was right up there with my best performances. I can see the changes already, especially in my body language, so long may it continue."
World number two Robertson agreed with that analysis and said: "A lot of frames went down to the last few reds and colours. If you get a bit unlucky with those coin flips, you can fall a few frames behind. I thought losing the first five frames was harsh.
“Mark's defensive safety was unbelievable in the match. He didn’t let up. He didn’t open up any of the frames.
“He got his game plan absolutely spot on. He kept it super tight and I couldn’t get any free-scoring going.

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“The frames were super scrappy with the black a lot of the time off its spot. Only 30 points were available when you came to the table unless you were producing great recovery pots.
“My safety game was one of the best I’ve ever put in, but when you are playing Mark I should have spotted the danger signs and opened things up a bit more.
“It’s better losing a frame quicker than playing a 30 or 40-minute frame and losing it.
“Each frame was so tightly contested. It was 13-7, but could have been the other way around."
Robertson overcame former English Open winner Liang Wenbo 10-5 in the first round and 2013 world finalist Barry Hawkins 13-9 in the second round, but feels he must address his Achilles heel at the event if he is to again claim the game’s top prize.

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The Melburnian’s top break against Selby was only 83 and his average shot time was a sluggish 30.5 seconds.
“The last six or seven years. I’ve not been losing to Judd Trump, Ronnie O’Sullivan or Shaun Murphy where it’s been open fare, it’s been really tight stuff where I’ve been knocked out of my rhythm,” said Robertson.
“I feel like I’ve got to take responsibility for that.
“I was playing way too slow when I was getting my chances because I was playing safety for 20 minutes and when you get a chance it’s hard to switch into free-flowing scoring mode.
“I didn’t identify the danger signs early enough. You’ve got to work out how not to be broken down. When a team puts 10 men and is camped in their box, you need to find answers for that.
“Mark’s safety was brilliant. Playing Barry and Mark over those four days, I probably played 35 frame-winning safety shots against anybody else in the world. And both kept finding escapes, playing unbelievable shots in return. It is tough going to keep coming up with answers.
“I felt I was right on the line against Barry of what was acceptable in terms of scoring, but against Mark I fell below that line and got bogged down too much. I couldn’t get out of it. You keep losing those 50-50 frames and it is hard to turn around.
“I’ve got to the quarters the past two years. It’s taken the two greatest match players of all time (John Higgins 13-10 in 2019) to beat me. You need to dispatch the players who make it difficult for you.
“I’m really happy with how I played, but the application was wrong.”
Robertson is remaining positive despite the disappointment of defeat and said: “The season’s been unbelievable. Four major finals and I’ve won three of them. I'm number two in the world. The last six months have been really tough on everyone, not just for snooker players.
“I was really happy to get the opportunity to play in the tournament.”
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