This was Alcarazs first tournament match since he won the US Open last month where he reached his No.1 ranking.
“David was playing really, really well. To come back to competition is never easy, Alcaraz said. Its really tough for me, for my confidence.
This is the first time that Alcaraz lost in straight sets since last year when he lost to Hugo Gaston.
Goffin started off quick and showed impressive pace and consistency.
“I always believe that I have the level to cause some trouble against those guys,” Goffin said.
“Of course, it has not been my best period, I haven’t been playing really well in the past few tournaments, but I always believe and practice and you never know.
“When you play against the World No. 1 on a big stage, big crowd, the fire inside gives you so much power to play your best tennis because you don’t have any choice. You have to fight and give your best and that was the case today.
I always believed I had it and I am happy you can still it there.”
This is not the first time that Goffins defeated a World No.1, he also beat Rafael Nadal when he was at the top of the rankings twice.
He is next set to go up against Adriana Mannarino.