Senegal's qualification is their first since the nation reached the quarterfinal at the 2002 World Cup.
"It wasn't easy for me, there was too much pressure on me but that has become normal", Mane said after the 2-0 away win over South Africa ensured progress to next year's Finals in Russian Federation.
The victory in Polokwane gave the "Teranga Lions" an unassailable lead at the top of Group D and with that their second appearance at the tournament.
Friday's match was a replay of an earlier World Cup qualifier between the two nations that was characterised by match-fixing allegations.
Bottom-of-the-table South Africa lie seven ponts behind Senegal ahead of a return match in Dakar next Tuesday, with Burkina Faso hosting Cape Verde at the same time.More news: 'Shots fired' as Lewis Hamilton's F1 team robbed at gunpoint in Brazil
"We brought on Andile Jali to try and break the lines even more‚ because they were playing deep and Lebo wasn't getting into the game very much".
Senegal joined Nigeria and Egypt as Africa's representatives at next year's World Cup, with three more spots still remaining for the continent at the global showpiece.
Mane's role as the talisman for Senegal has become increasingly evident throughout the qualifying campaign and there was a collective gasp of anguish when he injured a hamstring last month in the 2-0 away win over Cape Verde. On Saturday; Tunisia could qualify if they secure a point against Libya, whiles Morocco and Ivory Coast play for the fifth and final slot same day. We wanted to tell them that‚ "We know you've got famous players but we don't fear you - we want to get at you".
Senegal took the lead after 12 minutes when Sakho raced on to a Mane pass and side-footed the ball to the right of onrushing Khune.
Mane was also instrumental in the second goal, which was turned into the home team's net by their own defender Thamsanqa Mkhize.