Buchanan, an off-season signing from Bloemfontein Celtic, arrived at Naturena nursing a long-term knee injury.
The 25-year-old eventually made his debut as a substitute in a 4-2 victory on penalties over Maritzburg United in the last-16 of the Telkom Knockout on October 22.
Komphela then opted to field Buchanan ahead of Lucky Baloyi against Bucs in the absence of suspended midfielder George Maluleka.
"Keagan showed during training that he was ready and when a player is ready you don’t look at the opponent," Komphela told his club's website.
"I thought, ‘Derby or not, I will throw him in and we will see what happens.’
"Keagan did well and he can only grow from here and get better."
Meanwhile, Komphela said his team struggled to get behind Pirates' defence in a goalless draw at FNB Stadium.
"We tried to play a constructive game, but we struggled to get behind Pirates’ defence. Still, I feel we had the edge when it came to chances.
"With matches of this calibre, it’s often that you score a goal and you get a result."
The Absa Premiership leaders next face topflight rookies Baroka FC at Durban's Moses Mabhida Stadium on Wednesday (kick-off: 19h30).