Two-time world champion Michael van Gerwen had a pint thrown over him as he walked on for his first appearance at this year's tournament at Alexandra Palace.
The world No 1 was walking towards the stage when he was doused in the drink. The 29-year-old then headed backstage rather than to stage, the Daily Mail reported.
Van Gerwen, who looked upset when he returned, then regained his composure as he went on to win his match 3-1 against Englishman Alan Tabern.
After his victory, MVG still went back to the crowd to take selfies and sign autographs. Some supporters appeared to apologise for what had happened to him.
The culprit was thrown out and banned from darts for life. Speaking after his win, Van Gerwen said: "I was a little emotional. It's never happened to me before. I've never had this in my life.
"I didn't know how to react. I was angry. All I could do was change my shirt, wash my hands, it was all over me. On to the next round."