The Magician looked in the groove when he opened up a 5-3 advantage, but he was blown away by 25-year-old McGill on Sunday who won six of nine frames to triumph 10-8.
Defeat means Murphy’s wait to follow up his maiden Crucible victory from 2005 continues and also sees both of last year’s finalists beaten in round one for the first time.
But with partner Elaine O’Reilly expecting, the 33-year-old who grew up in Irthlingborough, was philosophical about his defeat.
“I’m disappointed. But the fact I have a child on the way has changed my perspective on a lot of things. It’s just a game of snooker,” he said.
“The baby is due at the end of August, so I’ve got plenty of time to get ready and whilst working on my long potting I will have to work on my nappy skills as well.
“I’ll still be practising just as much. My other half would have it no other way. She’d lock me in the snooker room if she had the chance.
“I came here to try and win, not to just try my best. That isn’t going to happen this year, so I have a little bit of unexpected time off but I will regroup and start next season as fresh as a daisy.”
McGill shot to prominence 12 months ago when he reached the last eight, but his progress was halted by Murphy who went on to reach the final.
Fast-forward to 2016 and a repeat looked on the cards. Murphy held a 5-4 lead overnight and was on for a maximum 147 break in the first frame on Sunday morning, though after sinking eight successive reds and blacks, opted to break the sequence in order to secure the frame.
But he sat glued to his seat as McGill kept his cool to win the next four frames in a row.
In truth Murphy barely played a loose shot, but could do nothing but applaud as his opponent made a break of 97 in the 18th frame to reach round two.
“We both played really well,” added Murphy.
“My preparation for the tournament couldn’t have been better. I came here in better shape than last year, but unfortunately I played against someone who was even better than I was on the day. It was a great match.
“We played here last year, but in snooker records and head-to-heads mean nothing. If he can keep his composure and play with enjoyment he could take some stopping this week.
“The way he finished the game off, what can I be disappointed with? I made two centuries of my own, won plenty of frames, my safety was very good and I’ve been beaten by a guy playing out of his skin.”
Watch the World Championship LIVE on Eurosport, with Colin Murray and analysis from Jimmy White and Ronnie O’Sullivan.