Swansea's 3-0 triumph at the Mestalla in the Europa League on Thursday was memorable enough in itself, but De Guzman's final goal capped off the evening perfectly.
The Dutch international midfielder, now in his second loan spell in south Wales from Villarreal, proved himself to be something of a set-piece specialist last season.
But the curling, dipping free-kick he produced from 30 yards to beat Valencia's Vicente Guaita topped any of his previous goals in a Swans' shirt, and he admits it was one of his best.
"I think it was probably one of the top three free-kicks in my career," he said.
"You don't score many goals like that, especially playing in a stadium like the Mestalla. It was a goal that was really special for me.
"I practice those type of free-kicks quite often - and I have been doing it ever since I was young.
"It is one of my weapons you could say. I have been taking set-pieces since I was a kid.
"In the academy at Feyenoord we practised it a lot. They groomed me there to take free-kicks and I took it with me."
De Guzman has previous experience of the Mestalla from his time with Villarreal and Mallorca, but could never have expected to enjoy such an emphatic result, which saw some bookmakers make Swansea their third favourites for the tournament.
But there is little time to dwell on European matters with a quick return to domestic action.
"It's remarkable," he said. "Playing against Valencia - it's a great team, a great atmosphere and a great stadium.
"They also have great players and I still think they have a great team. They have had an unfortunate start to the season and that helped us.
"It's funny having some people see us as among the favourites. We have made a great start, winning in Valencia, but there's a long way to go for us.
"I think everyone was shocked by the win. We just have to go on and try to do well in the next game. That's all we can think about for now.
"We are travelling again on Saturday. It will not be an easy game for us and it's new for us getting used to playing so many games."