Firpo's first competitive outing in a Whites shirt came as the left back was brought on at the break in last weekend's 5-1 defeat at Manchester United.
The 24-year-old then moved into the XI from the start for Saturday's clash against the Toffees as head coach Marcelo Bielsa made two changes to his side in also bringing in Kalvin Phillips from the outset.
That meant Stuart Dallas moving into midfield and left back Firpo quickly began linking up with Harrison on the left flank, seeing a cutback cleared in the second minute.
Not everything came off and Firpo lost possession when looking to find Harrison with a header in the third minute but the duo combined in a neat move four minutes later in which Harrison showed terrific skill.
His footwork was applauded by Firpo who took up a noticeably high position when Leeds attacked.
Firpo then stayed as the last man back at Leeds corners and defensively he was tasked with keeping tabs on Alex Iwobi when the Toffees moved forward.
Iwobi was kept reasonably quiet in the first half but it was Demarai Gray who burst clear down that flank in the 20th minute before sending in a low cross that narrowly evaded Dominic Calvert-Lewin.
Firpo then again looked to contribute in an attacking sphere and played a neat one-two with Mateusz Klich.
Shortly after, from a very advanced position as Leeds attacked, a loose ball bounced the way of Firpo on the edge of the box but a heavy touch as he looked to make inroads into the area meant a possible opening was gone.
His half ended with more pressing on Iwobi but four minutes after the restart Iwobi played a role in Everton going back ahead as he beat Firpo to Seamus Coleman's header towards the box from the centre circle.
Iwobi took one touch to control the ball just ahead of Firpo and then nudged a pass to Abdoulaye Doucoure who eventually played in Gray to squeeze home Everton's second goal.
Leeds, though, looked to quickly respond and Firpo again tried to contribute going forward in attempting a one-two with Harrison which was ultimately intercepted.
It proved his last act as the summer recruit was then substituted for Jamie Shackleton on the hour mark as Dallas moved back to left back.
In his 60 minutes on the pitch, Firpo had 54 touches of the ball and 31 of his 40 attempted passes were accurate, a success rate of 78 per cent.
The left back also won his sole attempted aerial battle and was successful with both of his attempted tackles.
In his place, Dallas quickly had an impact, as he does anywhere on the pitch. He is, after all, United's player of the year.
As for Firpo, these are still very early days but the left back was by and large defensively solid against Everton and it seems only a matter of time before something clicks in an attacking sphere.
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Thank you Laura Collins