Glasgow Warriors v Exeter Chiefs: Dave Rennie's side face 'mighty task'

Glasgow have beaten Exeter previously, but Stuart Hogg (left) has switched sides

At this time of year, it's standard practice for fans of teams on the bubble of qualification for the European Champions Cup quarter-finals to get out the calculator and pore over the permutations of what's required to make it.

The good news for Glasgow is that they need not addle their brain with arithmetic, for their task is obvious. The bad news is the task. It's a mighty one.

Having imploded after a promising beginning in Exeter in week two - a collective loss of plot led them to ship 21 points in a nightmarish third quarter - and after losing a home game in week four against a weakened La Rochelle, who had lost three out of three before coming to Scotstoun, Glasgow now need two bonus point wins in their remaining games to hit the number that is probably going to be required - 19.

Nineteen points usually gets you through. There are no guarantees that it will do the same this season, but Glasgow know that they probably don't stand an earthly unless they hit that mark. So 10 points from the next two games it has to be. In such an unforgiving tournament, this is the kind of brutal challenge you present yourself with when you butcher opportunities to pick up more points earlier in the group.

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On Saturday, the Warriors face their former full-back Stuart Hogg's Exeter Chiefs at Scotstoun, a team that not only sits atop the European Cup pool with four wins from four but also tops the Premiership table with six wins from eight. The two they lost were both by three points.

Exeter are not in the habit of losing. They're certainly not in the business of losing while conceding four tries. That's happened to them only eight times in 72 domestic and European games going back two-and-a-half seasons. Saracens account for three of the eight.

In that time, they've conceded one five-pointer in 16 European games. Leinster, Munster, Montpellier, La Rochelle, Castres, Sale Sharks and Gloucester all tried and none of them could do a job on Exeter to that extent. Glasgow are the only team to pull it off, not that it did them much good. They were already out of the running by the time they did it. And they had a mesmeric Hogg and an influential Finn Russell in their ranks that day. Such sorcery is thinner on the ground at Scotstoun now.

If this paints a picture of Exeter as a ruthless winning machine then that's precisely what they are. Fantastically driven and brilliantly coached, the Chiefs are more dangerous than ever this season. If Dave Rennie can orchestrate a five-pointer against this lot, even with home advantage, then it will be the best single-game achievement in his time in Scotland, bar none.

The Warriors are living through turbulent times. Rennie is leaving, assistant Jason O'Halloran is leaving, Scotland lock Jonny Gray is leaving (for Exeter in the summer). Fiji second row Leone Nakarawa is back on a short-term deal, but there's an unsettled air around Scotstoun. The place is needing a towering performance against the Chiefs to lift the mood.

Do they have it in them? You can build a case for them winning, but that extra bonus point? The strongest telescope would struggle to pick it out.

Dave Rennie needs his best single-game result as Glasgow head coach

When these teams met at Sandy Park at the end of November, Glasgow began well, causing Exeter problems in the scrum, denying them an attacking foothold and keeping them to three points in the opening 27 minutes. Glasgow led 13-10 at the break.

At that point, things were looking promising. Exeter's forwards hadn't had much of a chance to apply their suffocating pressure. Exeter's backs were living off bits and pieces. That changed dramatically in the second half when their unyielding aggression sparked panic in Glasgow, who produced some exit plays in their own 22 that suggested that their minds had gone. The Chiefs feasted on Glasgow's errors, scored three tries in the first 17 minutes of the second half and that was the game.

Once more, their forwards settled the issue. Exeter's pack is a lethal force. From close-range, their conversion rate is extraordinary. Since the beginning of last season, their pack has scored a total of 80 tries in Premiership and European rugby. The back-row delivered 34 of them, the front-row 27. The numbers are ridiculous.

Rennie knows what's in store if his team don't get on the front foot and stay there. Physically, Glasgow proved in the first match they have it within them to live with Exeter for 40 minutes. The also know the cost of not looking after the ball, of making poor decision, of not taking chances when they come along.

They need sustained and manic forward power and sheer brilliance out the back line to win this. Four points would be a wonderful return, but unless some strange results happen elsewhere over the next two rounds, they need five and another five away to Sale next weekend.

Glasgow put themselves in this position. Getting out of it will require something truly special.