The
10-8 victory was hard-earned, and Suljovic felt a mixture of relief and annoyance afterwards.
The sixth seed said: "It was a very hard game and I'm happy I won. I won so that's good but I was five legs ahead and I should have got it finished."
The Gentle notched up five 180s and two 116 checkouts. Smith replied with a 110 and a 130 during his comeback, but Suljovic prevailed with a 99.89 average.
"Michael is a very hard player so to be 5-0 up I was happy. I played well and my finishes were brilliant at the start," he said.
"At eight-eight I thought I would lose but the 116 was super. I showed some good form and I know that the next game will be very hard too because it's the 16 best players in the world."
Next up for the 2017 Champions League winner is a tricky quarter-final tie against world champion Rob Cross.
https://twitter.com/OfficialPDC/status/957090229902561280
https://twitter.com/MensurSuljovic/status/957007339860709376