Perhaps in knockout football, nothing ever matters apart from the result. You go through, you go out, the rest is noise. But that is especially true when the tie in question is the biggest rivalry in modern sub-Saharan African football. It was not the prettiest game, but it was never going to be, particularly given a pitch slippery with dew (and perhaps the 25 minutes of watering it took before kick-off).

Related: The journeyman French coach is fast becoming an endangered species in Africa | Jonathan Wilson

Not many people are going to be watching the full 90 minutes back with childish wonder. But it doesn’t matter. Nigeria go on to face Angola in the quarter-finals of the Africa Cup of Nations; Cameroon go home.

Nigeria were the better team. Victor Osimhen led the line tirelessly and with intelligence. Ademola Lookman took his two goals well. Alex Iwobi was the dominant figure in midfield. At the back, William Troost-Ekong was a colossus, entirely dominant against Frank Magri. That’s three clean sheets in a row now for Nigeria and the grumbles of fans and journalists are beginning to subside into grudging respect. Keep it tight and, where there is Osimhen, there is hope. “It was a hard game, an emotional game,” said the Nigeria coach, José Peseiro, “but we played with heart and controlled the game.”

Cameroon’s tournament essentially consisted of flurries in the final few minutes of games when panic drove them to unexpected heights. They troubled Senegal and came through the chaos of the finale against the Gambia but here, even after the introduction of Vincent Aboubakar, they offered little beyond the speculative, mustering no shots on target and only one corner. This is not a great Cameroon squad but Rigobert Song, their manager, is surely on borrowed time after the failure at the World Cup.

Song has been criticised for being little more than a figurehead while his assistant, Augustine Simo, arranges the tactics. “You have coaches and you have managers,” he said. “I am a manager, which means what it means. You do not coach a national team, you manage it.” But the toing and froing over André Onana hardly suggests decisiveness. After all the fuss, the Manchester United keeper played one game and didn’t make a single save.

In a tournament notable for an unusual openness, both Nigeria and Cameroon had seemed like throwbacks, ungainly giants playing in the style of a decade ago, all plugging gaps, keeping it narrow and compact and hoping for a set play or a flash of inspiration to generate something. This is a classic rivalry: since 1980, as Ghana have failed to live up to the glory days of CK Gyamfi, they have been the two most successful sides in sub-Saharan Africa, the only two African teams to win Olympic gold. Three times Cameroon have beaten Nigeria in Cup of Nations finals.

Angola's Gelson Dala scored twice as they reached the Africa Cup of Nations quarter-finals with a comprehensive 3-0 last-16 victory over neighbouring Namibia, who were left to rue four mad first-half minutes.

Angola, who claimed their biggest ever Cup of Nations finals win, had an early setback when the goalkeeper Neblu received a red card for handling outside the penalty area to stop a chipped shot from Bethuel Muzeu.

Namibia looked the most likely to find the net but the game turned when Gelson opened the scoring after 38 minutes, with a superbly constructed goal. Fredy was played into space on the right of the box and his low cross provided a tap-in.

The Namibia defender Lubeni Haukongo received a needless second yellow card shortly afterwards and the Angola forward completed his double from the resulting free-kick.

Angola added a third goal through Mabululu in the second half and now await a quarter-final tie against Nigeria, who beat Cameroon 2-0. Reuters

A derby atmosphere in a stadium that was pleasingly full, a sense of a game that, no matter what the outcome, would reverberate through the generations, two teams feeling for form, unsure of themselves and their place in the modern landscape … it was perhaps inevitable that it should be cagey.

That the opener, when it arrived nine minutes before the break, stemmed from a mistake was almost inevitable, but it still took awareness and unselfishness from Osimhen to make it. The Napoli striker scored only once in the group stage, missing numerous chances, but there is no doubt he is the key figure in this Nigeria attack. Having caught Oumar Gonzalez in possession, he showed great strength to hold off the midfielder and then, with the chance to shoot, laid the ball to Lookman whose shot squirmed under Fabrice Ondoa and, on the slick turf, slithered over the line as a desperate Gonzalez scrambled back.

• Download the Guardian app from the iOS App Store on iPhone or the Google Play store on Android by searching for 'The Guardian'.

• If you already have the Guardian app, make sure you’re on the most recent version.

• In the Guardian app, tap the Menu button at the bottom right, then go to Settings (the gear icon), then Notifications.

• Turn on sport notifications.

Lookman added his second from Calvin Bassey’s cross as Cameroon committed men forward late on. To say that after the opener it was a case of game management for Nigeria would be slightly misleading because it would imply they changed approach; rather the safety-first probing that seems their natural style under Peseiro continued to give them a sense of control while their threat remained limited to whatever Osimhen could forage.

Which might not have been much, but it was still more than Cameroon could muster.