ESPNscrum reporter Brett McKay analyses five key talking points of the weekend's Super Rugby action. Tell us your thoughts by leaving a comment at the foot of the page, and discuss the talking points with Brett on Twitter @BMcSport using the hashtag #ScrumFive.

Chiefs send a significant message

The best way to summarise the completeness of the Chiefs' 28-19 win over the Crusaders is to note their entire XV wouldn't look out of place in the Team of the Week tomorrow. But it wouldn't be because all 15 players had individually outstanding games; obviously, by definition every player can't stand out.

Rather, it was a classic case of the overall team performance being so much better than the sum of the individual performances. The Chiefs were, by some margin, the best team of round 15. Will they be the Team of the Week tomorrow? Well, no, probably not. My editor is unlikely to let me get away with it now that I've declared it a possibility.

Regardless, the Chiefs were able to force the Crusaders into making uncharacteristic errors across the board, and even into taking poor options. Kieran Read was outstanding in his return the previous week, but he was shut down rather effectively by the Chiefs' backrow. Aaron Cruden took the points over Dan Carter, and it was noticed during the game that the New Zealand commentators are now openly discussing the prospect of Cruden forcing Carter to second-five for the All Blacks.

The Chiefs showed tremendous composure throughout this brutal match, and particularly following the period when the television match official (TMO) disallowed a try in the second half. Chiefs teams of the past would've lost their bundle at that point, and piled on the unforced errors as they panicked themselves into trying to get similarly disallowed tries back.

Championships do tend to breed patience, though. The Chiefs calmly worked themselves back into position, took advantage of the opportunities the Crusaders defence presented, and were rewarded with the match-winning try to Bundee Aki - who coincidentally was the obstruction culprit in the earlier TMO ruling. The Crusaders have been one of the form teams in recent weeks, yet they had no answers for the questions posed of them. The Chiefs haven't necessarily been getting the press, but the message to other contenders was loud and clear.

Michael Cheika is a genius

You'll recall last week my mention of the New South Wales Waratahs coach not wanting to get too far ahead of himself, in terms of finals talk after his side accounted for the then competition-leading Brumbies. "I've learnt as a coach that predicting all that stuff only leads to disappointment," Cheika said at the time.

Cheika's refusal to entertain play-off thoughts was well and truly justified just six days later, with the Waratahs completely out-enthused by the young Melbourne Rebels, losing 24-22 at AAMI Park, and proving that a week is a long time in rugby. The loss drops the Waratahs into the "mathematical" category, and they'll essentially have to win every remaining game from here on - and with bonus points, probably - just to put themselves into the position where they could scrape into the last wildcard spot. If other teams above them fall in a heap.

It was simply the worst possible game in which to have an off night. Handling errors and ruck penalties made most of the Waratahs pain self-inflicted; they were literally their own worst enemy for most of the 80 minutes. The performance might yet reveal some harsh lessons for the Cheika game plan, too. There were several occasions during the game when the Tahs, without the game momentum, tried to run the ball out of their own quarter - when the better option would surely have been to play field position. Instead, their mistakes gifted even more momentum to the Rebels, who came home with the wettest of sails.

Cheika certainly deserves all credit for being able to turn around the Waratahs' collective mindset in less than six months. Consider how aesthetically pleasing they are to watch now, against what earned the wrath of their own supporters last year. The crowds will flock back to watch the Waratahs from here on.

It was hard not to enjoy the Rebels' win

Coming a week after they recorded the first victory over a South African side, the Rebels beat the Waratahs for the first time. In the club's history, it was just the third time in 45 games played that they've won two games in a row. Their evident excitement on full-time was well justified.

In the 72nd minute, they forced a turnover in their own half after the Waratahs had mounted 22 phases and had enjoyed 90% of the possession in the previous 10 minutes (according to the Fox Sports commentators). Fullback Jason Woodward made yet another line break to within five metres of the Tahs tryline, and a superb pass from fly-half Bryce Hegarty five phases later put lock Cadeyrn Neville outside his man, drawing in the winger and allowing a sensational offload to put Tom English over for his second try. That passage could in the future be recognised as a turning point for the club.

It probably can't be overstated, either, just how well the Rebels have played in the last fortnight in the absence of James O'Connor and Kurtley Beale. The self-belief in the squad is growing.

The concussion test cannot be taken lightly

Curious goings-on late in the Brumbies' impressive win in trying conditions in Auckland. In the 75th minute, outside centre Tevita Kuridrani stayed down after a tackle in which he appeared to have got his head in an awkward position. Play stopped soon after for an unrelated matter, but Kuridrani was very quickly and rightly in the hands of the Brumbies medic, Dr Angus Bathgate, and even began to leave the field under assistance. Suddenly, though, and perhaps coincidentally, time was called back on, and Kuridrani could be seen motioning the medics away while he ran back to take his place in the defensive line.

To his credit, referee Lourens van der Merwe checked with the Brumbies medicos, having obviously noticed the earlier concern about Kuridrani's state. Van der Merwe even questioned if Kuridrani was going off to have a Pitch-Side Concussion Assessment (PSCA), but then strangely declared he wouldn't be held responsible should Kuridrani prove to be unfit to continue playing.

Dr Bathgate replied that Kuridrani had "passed the test", and that they would continue to monitor him over the next two minutes.

There's all sorts of alarm bells in this for me. For starters, the whole point of the PSCA is to ensure players can be assessed properly, well away from the temptation of the game, and the laws allow teams a free temporary substitution to do so. The test is in place because player safety is paramount, and also so that teams aren't disadvantaged by having to use one of their seven replacements.

I'm not for a minute suggesting that Dr Bathgate acted anything but professionally, and likewise I obviously don't know what "the test" on field comprised, but surely in this situation, when the referee had recognised the state of the player enough to audibly attempt to absolve himself of responsibility for the player's welfare, the duty of care should extend beyond asking the medics if they want to conduct the PSCA, but to actually ensure they do? Head injuries are not trivial, and the situation of a game should not dictate how they are handled.

'Spoiler' teams confirmed

We're at that point in the season when teams move from being a "possible contender" to become a "mathematical chance" of making the Super Rugby finals. All number of different permutations will be raised to highlight how a team can make the play-offs, and the teams benefitting in any calculations are generally determined by the allegiance of the person counting the fingers.

In reality, once a team drops into the mathematical category, their actual chance of qualifying is slim. These teams then become "spoilers", capable of causing damage to teams ensconced in the top six.

Teams needed 57 or 58 points in the past two seasons to make the top six (and even that wasn't enough for the Brumbies last year), meaning sides that still don't have 40 competition points now will have a hard time getting there over the remaining rounds.

The Stormers got in early on the spoiling, with their 20-15 win over Queensland Reds putting a major dent in the Australians' hopes of leap-frogging the Brumbies into top spot in the Australian conference. The Stormers can similarly upset the plans of the Cheetahs in round 18, and the Bulls in Cape Town in the final round.

The Sharks pushed the Bulls all the way in Durban on Saturday night, and they get another chance to take points off the Bulls in Pretoria in round 19. They play the Blues in round 18 before that.

The Hurricanes have four games remaining, with three against sides currently in the top six: the Brumbies this Friday night, the Chiefs in round 18 on the resumption in late June, and a final-round clash with the Crusaders.

The Waratahs round out the "spoilers", and they will cause significant damage should they upset the sixth-placed Crusaders on Friday night. Beyond that, their final-round showdown with the Reds in Sydney could well determine whether Queensland see play-off action or not.