The Sharks made heavy weather of their 20-10 triumph against the Jaguares but it booked them a quarterfinal spot.
Unlike last week, they made the most of the Rebels' 43-37 loss against the Highlanders but they weren't convincing.
The Jaguares, already assured of a playoff, will face the Lions and the Sharks earned a date with the Crusaders in Christchurch. The defending champions are unbeaten at home.
The Sharks have an outstanding record against New Zealand sides this year but the Crusaders haven't dropped a game at home in two years and have lost just six home matches in five years.
One of those defeats was against the Sharks in 2014, one of only two South African Super Rugby wins in the South Island rugby stronghold in 22 years.While the cold, wet conditions weren't conducive to fluent rugby, the Sharks struggled to put together meaningful momentum against a second-string Jaguares.
Despite their disappointing loss to the Bulls last week, the Jaguares gave their bench a decent run knowing a sterner test awaits at Ellis Park.
While they clearly lacked motivation, they made up for that with reasonable endeavour as they dominated the statistics.
They did not have a try to show for their first-half efforts but were robbed of a penalty try in the 39th minute when Curwin Bosch clearly held back Matias Moroni after the Sharks coughed up possession in their own half. The ball narrowly beat Moroni to the dead-ball line and the Sharks breathed a massive sigh of relief.
Amazingly, the Sharks scored the only try of the first half through explosive hooker Akker van der Merwe in the 22nd minute while they were a man down.
While Van Der Merwe broke away from a maul to score, No8 Daniel du Preez was sin-binned for a chop-tackle on Jaguares lock Tomas Lavanini.
The scrappy nature of the game didn't change in the second half even though the sides scored brilliant tries.
Sharks (13) 20
Jaguares (3) 10
Sharks: Tries: Akker van der Merwe, Kobus van Wyk; Conversions: Robert du Preez (2);Penalties: Du Preez (2))
Jaguares: Try: Sebastian Cancelliere;Conversion: Joaquin Diaz Bonilla; Penalty: Joaquin Diaz Bonilla..