It's coming down to the crux of the matter - two weekends in which teams from all over Europe can compete for the Heineken Champions Cup, or pack up and go home.

This weekend it's Round 5, and there is so, so very much on the line. Leinster, defending champions and so dominant in the Guinness PRO14, will take on unbeaten Toulouse on Saturday, and that's just the beginning.

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Toulouse can clinch a place in the quarterfinals by winning and also denying Leinster two bonus points. The victory would also make Toulouse 3-0 on the road in the Heineken Champions Cup. Realistically, Leinster could still lose and make the quarters as one of the best three second-place teams. But the Irish squad would much rather win and take a shot at 1st.

Edinburgh could make history by beating Toulon on the road for the first time ever. A win there, and a loss by Montpellier would clinch Pool 5 for the Scottish team. As Edinburgh's Juan Pablo Socino said in his column for FloRugby, "the team is highly motivated, understanding what lies ahead."

Conversely, Montpellier takes on Newcastle and needs to win, and would very much like Edinburgh to lose in Toulon, which could then set up a winner-take-all clash next Friday between Montpellier and Edinburgh.

Glasgow Warriors welcome the Cardiff Blues, who will likely be without USA star Blaine Scully, who was injured last week. Glasgow is in excellent position to get into the quarters even if Saracens win (as expected) against Lyon. 

Right now Leinster, Glasgow, and Ulster have the best records of the five second-place teams.

Unbeaten Racing 92 can clinch a quarterfinal spot with a win on the road against Ulster, and even if that doesn't happen, Racing should do the job next week at home against the Scarlets. If Ulster can secure two wins, then a quarterfinal place is assured. One win probably does it.

In Pool 2, Munster, Castres, Exeter, and Gloucester are separated by four points in the standings. It's highly unlikely that the second-place team will get to the QFs, but any of those four could win the pool.

Friday it's Gloucester hosting Munster is a massive clash. Gloucester is fourth out of four in the pool, but at 2-2 isn't out of it. A defeat of 2-1-1 Munster could flip the script. Both Castres and Exeter want a Gloucester win, too, as that helps those teams in the chase for 1st.

Gloucester faces Castres next week, and Exeter takes on Munster and there's a very real possibility that all four teams will still be in with a shot. However, if Munster wins at Kingholm Friday, the Irish will control their own destiny.