Nigeria eliminated holders Cameroon in the last 16 before knocking out South Africa, the conquerors of hosts Egypt
Nigeria coach Gernot Rohr admitted he expects a far tougher challenge against Algeria in Sunday's Africa Cup of Nations semi-finals than during qualifying for the 2018 World Cup.
The Super Eagles finished top of a section including 2017 African champions Cameroon and Algeria on the road to Russia last year, defeating the Desert Foxes 3-1 at home before a 1-1 draw in the return fixture.
Algeria were later awarded a 3-0 walkover for the second game in Constantine after Nigeria fielded an ineligible player, and Rohr has been impressed by their improvement since Djamel Belmadi took over last August.
"He's done a very professional job. They were shaky at the time. We beat them 3-1 (in Uyo) and they made lots of individual errors and defensives mistakes that made it easier for us to win. They were also fragile in the draw," Rohr told reporters Saturday.
"Now I see a solid Algeria side with a good balance between attack and defence. They're still physical but they have come on since and it will be a much harder match than in World Cup qualifying."
Nigeria eliminated holders Cameroon in the last 16 before knocking out South Africa, the conquerors of hosts Egypt, in the quarter-finals in their first Cup of Nations since lifting the title for a third time in 2013.
Rohr's side have bounced back strongly following a shock 2-0 loss to Madagascar that cost them top spot in their group here, leaving the German confident they can overcome an Algeria team that has scored 10 goals in Egypt while conceding just once.
"As coach you're always optimistic. We know they're a good side but we have a strong team too. We can reasonably hope to win based on our last two performances but we're wary because of our opponents," said Rohr.
"We still have things to improve, for example if we have chances to score a second goal we need to be more clinical. They've been more impressive than us on the whole so far."
Nigeria had one day's rest more than Algeria, who needed extra time and penalties to squeeze past Ivory Coast on Thursday, but Rohr doesn't believe that will play a factor in Cairo.
"To have one day more to recover could in theory be an advantage but practically speaking I don't think so. We were in the same position against Madagascar, we had two days extra but we lost the match," he said.
"All teams are prepared to recover quickly. They all play at good clubs and have good physical trainers too. I think the fatigue soon goes."