Super Rugby Round 18 preview: Who secures a finals spot?

We've reached the final round of the regular season, and it could be the most exciting yet, with at least eight teams remaining in contention for a playoff position.

The weekend kicks off with two blockbuster trans-Tasman clashes -- Highlanders vs. Waratahs, and Rebels vs. Chiefs -- with both matches possibly impacting the top eight, while two crucial South Africa derby clashes -- Stormers vs. Sharks, and Bulls vs. Lions -- round out the action to determine who reaches the playoffs.

Read on for some of the key storylines to keep an eye on this weekend.

AUSTRALIAN CONFERENCE

Rebels star lineup must turn up

The Brumbies have secured their place at the top of the Australian conference and therefore a top-three finish and a home quarterfinal, and the Rebels and -- mathematically -- the Waratahs are still playing for the chance to reach the playoffs.

Sitting third on the combined table, the Brumbies have a chance to move up to second spot and earn a home semifinal (if they're to move to that stage), but they must beat the Reds -- which should cause no issues -- and rely on the Sunwolves recording perhaps the biggest upset of the season in toppling the Jaguares in Buenos Aires; the latter is not likely.

Realistically, then, all eyes will be on the Rebels and their hopes of securing their first playoff berth with a win over the Chiefs at home.

Sitting eighth on the table, the Rebels require a win to keep their season alive. If other results go their way -- Bulls draw and Sharks win or draw -- they can potentially move up to fifth place and avoid a quarterfinal showdown with the Crusaders. But let's not get too far ahead of ourselves; simply defeating the Chiefs will be a task in itself.

For everything to fall into place for the Rebels, they need to shrug off last week's horrendous performance in Christchurch; the question of whether they can do that will be determined by the resolve of their experienced campaigners Quade Cooper, Will Genia and Matt Toomua.

With Cooper moved to the bench and Genia rested through the Wallabies policy last week, the Rebels pulled out one of their worst performances of the season; their defence was torn apart, and their attack succumbed to pressure. They were clumsy and their game was hampered by errors as they missed 38 tackles and let in 10 tries, while Toomua struggled to create anything with the little possession the side earned. It was an embarrassment to watch, and only a complete turnaround can keep their season alive.

While Genia's return to the lineup alongside Marika Koroibete, and Cooper's return to the starting XV, should boost the under-performing side, their 2-6 record in their past eight matches speaks against them. Cooper must return to his dazzling best, with his flashy backline play absent over the past month, while Genia must also pick up his performance to give his side a chance -- his kicking game especially.

Meanwhile, the Waratahs mathematically have a chance to grab a wildcard place, but they need everything to go their way -- especially with five of their Wallabies rested for the final round of the season.

After their disappointing 35-24 loss to the Brumbies, the Waratahs must record a bonus-point victory in the first game of the round and hope for later results to go their way -- including the Chiefs winning without a bonus point -- to secure a wildcard spot. But after Daryl Gibson rolled the dice during the season, and refused to rest Wallabies stars Bernard Foley, Kurtley Beale, Michael Hooper, Sekope Kepu and Rob Simmons in earlier rounds, he's been left with a motley crew to get the job down in Invercargill. Waratahs fans, don't get your hopes up.

While it seems simple, a win from the Rebels will see them in the top eight; but a slip up could see them miss another finals opportunity, and leave just the one Aussie side playing for the Super Rugby title.

NEW ZEALAND CONFERENCE

Simple equation for Chiefs, but not easy to accomplish

The Crusaders had their fair share of wobbles in 2019, but still they locked up their position atop of the ladder weeks ago; the Hurricanes, meanwhile, secured their top-four position last weekend after a topsy-turvy year. But the Chiefs and the Highlanders still have plenty to play for.

The Chiefs battling through injuries to pull their season back from the brink after a horrendous start to the year and a midseason winless run to sit just one point outside the final eight; they've done well just to have a chance to squeeze their way into a playoff spot.

Still if the Chiefs were to defeat the Rebels with a bonus point, with a points difference of +46, the Lions were to lose without a BP, and the Stormers were to draw, they would rise as high as sixth on the table. If that permutation was a bit mind bending, wait until we get to the Highlanders!

But let's keep it simple. To keep their series alive, the Chiefs must secure a bonus win over the Rebels in Melbourne. Simple.

The Chiefs have secured just one BP win all season, however, and they have the second-worst defence of the competition having given up the second-most tries and penalty goals.

But with All Blacks star Brodie Retallick set to return after nine weeks on the sideline, they have a strong chance. Taking on the Rebels a week after the Australian side's 66-0 drubbing by the Crusaders may be a blessing or a curse but that can only add extra spice to the clash.

If the Chiefs were to earn a wildcard spot after failing to secure their first win of the season until round six, it'd be a further reflection of just how tight this Super Rugby season has been and how much work has gone into turning their year around.

The Highlanders face a much more difficult task to reach the playoffs, however; so much more difficult that it can be placed in the 'unlikely' category.

Sitting 11th on the table, the Highlanders need a lot of things to go their way if they're to secure a wildcard spot.

Firstly, the Highlanders must win and claim a bonus point; if they don't, they're out the door. Second, the Lions must lose to the Bulls without claiming a bonus point; and third, the Chiefs must win without a bonus point. If that has you scratching your head, it's understandable.

Put simply, a win with a bonus point is the only way to keep the Highlanders season alive. And everything seems to have just become a lot harder.

Fullback Ben Smith has been ruled out -- and is unlikely to play for the side even if they do reach the quarters; rain has been pouring down in Invercargill throughout the week, with more forecast; and the Highlanders have secured just the one bonus point win this season, in their 52-0 romp over the Sunwolves.

They will need to be disciplined and patient, and if the Waratahs are to score just one try on Friday, they will need to work that much harder to secure the four tries needed for the bonus point.

While the young Waratahs team are expected to struggle in the wet, the Highlanders themselves usually play in dry conditions undercover at Forsyth Barr Stadium and will need to change their own game plan, giving the side plenty more to think about.

However, if the Highlanders can exploit the Waratahs youth and inexperience, they should set up a long weekend of screen watching.

SOUTH AFRICAN CONFERENCE

Sharks hoping Robert Du Preez has found his kicking boots

Four teams featuring in two derbies, the winners of which are guaranteed finals football; not only derbies to conclude the home-and-away season, but the key South African rivalries -- the Jukskei Derby between the Bulls and the Lions, and the Coastal Derby between the Stormers and the Sharks.

And all four teams can make the playoffs.

The Bulls, Lions and Stormers are currently in the post-season berths, with the Sharks ninth on the overall log, just a point behind the Stormers and boasting a better points differential than three finals contenders above them, and two of the three contenders beneath them on the table.

And that's about as good as it could be in South Africa, after a season of stop-start performances that have delighted and confounded pundits and fans alike, often within the same 80 minutes. Each of the South African teams have impressed at times; each have disappointed at others. We can debate their standard of play, the quality of the game plans, all we like; but they are where they are on the ladder because that's where they deserve to be compared with their 11 rivals on the log, and discussions about the quality of Super Rugby outside the top four, who are head and shoulders the best teams in the comp after 15 rounds, are best served for another day.

The best thing for the South African teams is that all four will know at kick-off exactly what they must do to secure post-season footy; that's the advantage of playing the final two games of the round. Right now, however, the only certainty is that the Sharks must beat the Stormers in Cape Town if they are to secure a finals berth. And they must do so with Robert du Preez at fly-half.

Du Preez has become a lightning rod for much of the angst about the team, with the Sharks coach, his namesake father, either selecting him in preference to Curwin Bosch, or replacing the latter and moving him to fullback and benching Aphelele Fassi.

This selection when made through the season has caused much disaffection among Sharks fans, and confused the South African rugby community more broadly, because du Preez simply has not performed well enough to deserve selection. Bosch may well be a better fullback than a fly-half, but he's also performed better at fly-half than has du Preez.

The coach was spared another difficult press conference when Bosch was ruled out with an ankle injury, but his reasons for picking his son and benching Fassi against the Jaguares in Buenos Aires last week suggests he may well have made the same picks this weekend.

"In the game against the Jaguares, we needed an experienced 10 and 15 because the thought process was that the game was going to be like a Test match,' Du Preez said on East Coast Radio during the week."With both players having played at the highest level and both having a great kicking game and decision-making, I felt we needed both on the field and that was the reason behind the selection."

This week's game is even more important, and these words from the coach will be ringing in his son's ears in Cape Town.

"This weekend is a big one and he knows what is at stake and what is expected, and so does the whole team. It won't come down to one guy, it's going to be a team effort from all 23 players."

The last sentence rings truest: "It's going to be a team effort from all 23 players."

For all du Preez's inconsistencies and lack of form, the Sharks have not been outperformed in their disappointing performances because he has been the No. 10; they've often been outmuscled up front, and that has had nothing to do with the pivot. Nor has their attack offered much greater thrust with Bosch at 10, much as he's a more rounded footballer.

The Coastal Derby will be physical - they always are - and it's hard to envisage either side being truly brave with ball in hand given there's so much at stake as that really isn't in South Africa's rugby DNA.

Neither side has been prolific this season - the Stormers scoring 335 points and 34 tries compared with the Sharks' 331 and 38. Hence this game is likely to come down to goal-kicking.

Robert du Preez's stats off the tee this season?

He's kicked 10 penalties and 15 conversions at just 71 percent; Bosch, meanwhile, has kicked at 82 percent this season, while the Stormers' Josh Stander has made 20 of 23 attempts.