While the previous five last-16 ties had produced a heady mixture of shocks, drama and comebacks, Sunday’s match was straightforward as Algeria, yet to concede a goal at the tournament, won their fourth straight match.
The Desert Foxes were strong in defence, intelligent in midfield, ruthless in attack and played with a swagger that suggested they believe they are on course to lift the cup again.
Belaili broke the deadlock after playing a one-two with Baghdad Bounedjah in the 24th minute and Mahrez, following some sublime control, lashed home the second just before the hour.
Substitute Adam Ounas added the third on the break in the 82nd minute, making him joint tournament top-scorer with three goals alongside Senegal’s Sadio Mane and Nigeria’s Odion Ighalo.
Algeria, whose one previous title came in 1990, will face either Ivory Coast or Mali in the quarter-finals, and coach Djamel Belmadi was not worried about their favourites tag.