The 21-year-old had previously shown plenty of promise for Bafana Bafana without finding the back of the net or providing an assist, but delivered a standout performance to help Pitso Mosimane’s side secure a second consecutive Group D victory.
Mofokeng had already struck the post before breaking the deadlock in the 19th minute. Oswin Appollis found him with a precise pass and the attacker calmly controlled the ball before slotting into the bottom corner.
He doubled the advantage just before half-time, collecting a pass from Samukele Kabini before weaving past defenders and finding the net again.
South Africa had to reshuffle early after Bathusi Aubaas was forced off with a knock, with Brooklyn Poggenpoel making his international debut.
READ: AFCON qualifiers: Pitso Mosimane Wary of Eritrea Threat Despite Bafana Bafana’s Positive Start
Eritrea threatened at times, particularly on the counter-attack, while Ronwen Williams was also called into action after an uncertain opening spell. The Bafana captain later produced an excellent save to deny Esrom Yohannes.
South Africa, however, took firm control after the break.
Sphephelo Sithole made it 3-0 in the 52nd minute after Eritrea goalkeeper Yonathan Sultan parried an Appollis effort into his path. Rayners then added a fourth 11 minutes later, smashing home from a tight angle after another assist from Appollis.
Appollis completed an outstanding evening with his third assist in stoppage time, crossing for substitute Luther Singh to finish from close range.
The victory gives Bafana six points from their opening two qualifiers after Saturday’s 2-1 win over Guinea, putting Mosimane’s side firmly in control of their early campaign.
Mofokeng’s brace also marked an important breakthrough for the young attacker, who had previously been recognised mainly for his potential but now has his first two senior international goals.