Goffin overcame an injury-hampered Dominic Thiem 6-4, 6-1 at the O2 Arena to book his place in a first ever semi-final at the ATP World Tour Finals.
The Belgian will now face Federer for a place in the final, an opponent to whom he has lost every single time in six meetings.
“I’ve never found a key to beat Roger,” Goffin said.
“Honestly, I don’t know what to do tomorrow.
“But I’m going to try something, something different, something that I’ve never done in the past.”
Their most recent meeting came last month at the Swiss Indoors, when Federer thrashed Goffin 6-1, 6-2.
And having already undergone one comprehensive straight-sets defeat – 6-0, 6-2 to Grigor Dimitrov on Wednesday – the Belgian is determined to right the wrongs of that day.
“I will try to do my best to play a better match than in Basel, for sure,” Goffin added.
“In Basel, it was not easy. He played well. He didn’t miss.
“He was really aggressive, as always. He returned so well. So it was not easy in Basel.
“I hope that tomorrow he’s not going to play the same match.
“But I will try something different for sure.”
Federer meanwhile did not watch Goffin’s win over Thiem, instead opting to remain in west London and hit at the Queen’s Club.
The Swiss spent time on court with 18-year-old Miomir Kecmanovic before an hour working with coaches Ivan Ljubicic and Severin Luthi.
