What's at stake and for who ahead of the final round of regular Top 14 season

Two of the northern hemisphere's leagues - the Premiership and Pro14 - have entered the play-off phase, but rugby's most gruelling competition still has one more weekend to run before it is cut from 14 to six.

Three Top 14 teams can relax. The top two, Toulouse and Clermont, have already earned themselves a week off by qualifying direct for the semi-finals in Bordeaux, so can sit back and watch four teams become two next weekend.

Lyon, meanwhile, will be involved in the qualifying play-off barrages for the right to travel to Bordeaux for the semi-finals. They have earned themselves home advantage for that one-off play-off.

That leaves four teams - Racing 92, reigning champions Castres Olympique, Montpellier, and La Rochelle -separated by three points, chasing the final three all-important play-off places ... which grants them a shot at the Top 14 title and Champions Cup rugby next season.

Here are the games that really matter in the Top 14 in the final week of the regular season - when all seven matches kick off at 4.15pm (France time) on Saturday.

Agen (12th - 38pts) v Racing 92 (4th - 69pts)

On paper, this looks simple enough for moneybags Racing. But, despite their lowly league position - and because of their loss at home last weekend to Racing's play-off rivals Castres - Agen have a point to prove. They'll want their fans to go into the summer with a smile. This could be more difficult than many expect for the visitors - but even a defeat would not be entirely disastrous ... unless Racing fail to get a bonus point and their play-off chasing rivals all win...

A note: A 'home' barrage match is out of the question, even if Racing hold on to fourth spot, which promises home advantage. French popstar Mylène Farmer is due to play nine shows at La Defense Arena between June 7 and June 22, and will be deep into rehearsals on barrage weekend of May 31 / June 1. If Racing are 'at home' for their play-off qualifier, they will relocate to their former home at Stade Yves-du-Manoir, Colombes.

Castres Olympique (5th - 69pts) v Toulon (10th - 53pts)

Last year, Castres became the first team to finish in the sixth and final play-off spot that then went on to lift the Bouclier de Brennus. This year, they should have ensured their place in the end-of-season knockout phase before last weekend's crucial play-off saving win at Agen.

But they snatched defeat from the jaws of victory in back-to-back run-in home matches against Toulouse and Montpellier to ensure their play-off challenge became more difficult than it needed to be. Even so, their future remains in their hands. A win ensures a top-six finish. A draw or a defeat, however, leaves them watching results elsewhere, nervously.

Clermont (2nd - 82pts) v Montpellier (6th - 66pts)

You can't ignore who they're playing, but this game is all about Montpellier. All-but out of the play-off reckoning a couple of months ago, Vern Cotter's side have won seven of their last eight games - the one blot on their recent copybook a one-point loss at Racing 92 - and moved back into the top six for the first time since October with a last-gasp bonus-point win over Stade Francais.

Their record against La Rochelle this season has given Montpellier a crucial advantage going into the final weekend of the regular season. Match or better the Rochelais and a play-off place is theirs for the taking. A home barrage is not yet out of the question, either - for Montpellier or La Rochelle. But, you can't ignore who they're playing.

La Rochelle (7th - 66pts) v Bordeaux Bègles (9th - 57pts)

Different league, definitely not different rules. This is the match Sale fans should watch very closely. If La Rochelle can get themselves back into the top six after dropping out last week, the Premiership side will qualify for next season's Champions Cup.

The Rochelais have already booked their seat at Europe's top table next season, by virtue of being losing Challenge Cup finalists to Clermont, whose qualification by Top 14 league position supercedes their qualification by Challenge Cup victory. But La Rochelle have French title ambitions so will be keen to ensure their interest continues beyond this weekend.

Opponents Bordeaux blew their outside chances of qualification when they let slip a bonus-point win at home to Toulouse to finish with nothing from a game in which they had scored five tries. Frankly, they'll be mad, and not in the mood to let their Atlantic coast rivals have it all their own way, even at Stade Marcel Deflandre.

The complicated bit

So far, so straightforward. But now the maths gets complicated. Fourth-placed Racing have the advantage over all three play-off rivals courtesy of one-on-one results this season against the three other sides in case they finish the season level on points.

Past results, meanwhile, this season favour Castres over Montpellier if those two sides finish level on points, but if La Rochelle and Castres both finish their campaigns with the same number of league points, the Rochelais will finish higher than the defending champions.

Got that?

Whatever happens, the side that finishes third will host the sixth and final placed side in the barrages, while the side that finishes fourth will play the one that ends up fifth on the weekend of May 31 / June 1.