Up until last season, the teams that emerged from the round of 16 to play in the quarter-finals did it by winning a double-legged tie, meaning home and away fixtures with the winner determined on aggregate score across the two games. With a home fixture guaranteed, the finishing order didn’t matter so much.

However, under the current format that changes markedly, the top four teams on the final log in the respective pools will be hosting their one-off round of 16 fixtures, with the teams finishing from positions 5th to 8th in the pools having to travel.

And with the play-off games that follow the round of 16 all being hosted by the higher ranked team, with one caveat, this weekend’s games have huge significance. The caveat is that the South African teams will have to host their semi-finals overseas should they progress, with the final set for Dublin regardless of who gets there.

An example of why this weekend is so important can be understood by looking at the possible South African scenario.

If the DHL Stormers and the Vodacom Bulls - with the Capetonians currently fourth in Pool B and the team from Pretoria sixth in Pool A - win their final games this weekend, there is a good chance that we could see a replay in Cape Town of last year’s Vodacom United Rugby Championship final in the round of 16.

Conversely, if the DHL Stormers slip or drop points in their final pool fixture against Clermont-Auvergne on Saturday evening, they could find themselves traveling to Pretoria, or worse still to somewhere like Saracens or Exeter Chiefs, or even Dublin to play Leinster if it goes really bad for them.

Any of those latter fixtures would be far less palatable to Steven Kitshoff’s men than a home game against either the Vodacom Bulls or, as the log stands currently, the Edinburgh team they beat fairly easily at DHL Stadium in last year’s Vodacom URC quarter-final and again in a league fixture earlier in the current season.

Neither the DHL Stormers nor the Vodacom Bulls have officially booked their places in the last 16 and could theoretically still fall out of the picture completely if they lose badly at the weekend.

However, with the Stormers playing at home, you’d fancy their chances of at least keeping the points differential advantage they have on other teams in order to make their passage to the next round safe, and the Bulls are also well placed on points differential in comparison to teams that can catch them on log points.

The Cell C Sharks have a lot more to play for on their trip to London to face Harlequins on Saturday than you’d imagine was the case, seeing they are the one South African team that have already qualified for the round of 16.

The Durbanites are currently seeded second in Pool A, and if they hold onto that position, they will have a good chance of securing home advantage for both the round of 16 and the quarter-final that will be played a week later. For them, a win this week at The Stoop will be a significant step towards possibly making the semi-finals.

So this is effectively the weekend that could make or break challenges as it will determine home advantage not just for the first play-off phase, but also the rankings that will impact on who plays where beyond that.

In that sense there are some interesting match-ups this weekend of crucial importance, with only one point separating Leinster, the Sharks and Saracens in the quest for the advantage that comes with pole position in Pool A, and with three teams - Toulouse, Stade Rochelais and Leicester Tigers - locked together on 13 points in Pool B in the battle for top spot there.

The DHL Stormers are theoretically still in with a chance of topping Pool B, which they would do if they scored a bonus point win over Clermont at the DHL Stadium and Toulouse, Stade Rochelais and the Tigers lost their last pool games. Those teams are currently three points ahead of John Dobson's side on the log.

As it stands now, the Cell C Sharks will face an interesting round of 16 match against French champions Montpellier, who are down the log in Pool B after two successive losses to the Ospreys.

The approach to the pool phases of the Heineken Champions Cup is for some French teams impacted by the bunfight they are involved in trying to avoid relegation from the Top 14. Two teams get dropped at the end of every French league season, and currently none of the teams positioned from fourth through to 14th are safe.

But that might change by the end of March, and if Montpellier feel safer in the Top 14 they might be a more formidable proposition in the round of 16. The same goes for most other potential French opponents.

Weekend Heineken Champions Cup fixtures

Friday, 20 January
22h00: Lyon v Vodacom Bulls
22h00: Leicester v Ospreys

Saturday, 21 January
15h00: Northampton v Stade Rochelais
15h00: Harlequins v Cell C Sharks
17h15: Bordeaux-Begles v Gloucester
17h15: Leinster v Racing 92
19h30: Exeter Chiefs v Castres
19h30: DHL Stormers v ASM Clermont-Auvergne
22h00: Ulster v Sale Sharks
22h00: Montpellier v London Irish

Sunday, 22 January
17h15: Toulouse v Munster
19h30: Edinburgh v Saracens