Blessed with the benefit of Gallic home advantage, the EPCR Win Predictor estimated that Montpellier had an 81% chance of victory based on their individual quality.

However, the physicality of Ospreys’ pack prevailed to deliver a decisive victory in Round 2 last month.

Ahead of the two sides’ Round 3 clash in Swansea on Saturday, we take a look back at how the Welsh region clinched a surprise first win in Pool B.

The swing of the win predictor in Ospreys’ favour around the hour mark was clearly the decisive momentum shift for the visiting side – who had steadily improved their chances of winning but consolidated their ascendancy with their third try, courtesy of Morgan Morris.

This try begins with a Jac Morgan tackle turnover in the 59th minute. This action alone – due to its position on the field and the moment in the game – takes Ospreys from a 45% likelihood to win to 50%.

After a few phases of Ospreys play, Montpellier No.8 Zach Mercer concedes a penalty. Ospreys were gathering momentum at this stage, up to a 57%-win probability.

Finishing in the corner after a strong lineout maul and a couple of powerful carries, Morris’ score made his side the clear odds-on favourite to see out the match at 82%.

This momentum shift was built on two pillars: Ospreys’ ability to win possession in the tackle and their maul. These were the motifs of their outstanding performance.

So far in the Heineken Champions Cup, last season’s United Rugby Championship (URC) Welsh Shield winners have made more choke tackles than any other team (20), with Justin Tipuric accounting for a tournament-leading five of these.

Against Montpellier in particular, the Ospreys made ten choke tackles – all slowing down speed of ball and producing two turnovers.

What is especially impressive is that players across the pitch have bought into this defensive strategy. In the opening two rounds, Alex Cuthbert and Owen Williams have made three and two choke tackles respectively – the former is the highest total for a back.

Bravely challenging the oncoming Henry Thomas, in this example Owen Williams and Ethan Roots extract a crucial tackle turnover from Montpellier – who have either scored a try or been awarded a penalty during a league-high 57.4% of their 22 visits in the TOP 14 this season.

Critical to the success of this tackle is the speed of Ospreys forwards to support Williams. A tighthead prop running at a fly-half, Thomas backs himself to win the collision; Williams is happy to concede a couple of metres but keep the attacker off the deck, giving the heavy mob time to support him.

This turnover concluded the first half and saw Ospreys carry both momentum and an 11-point lead into the second period.

In terms of the maul, the success of the Swansea-based side was based on their manipulation of the ‘6+1’ lineout, meaning six in the line with a forward in the scrum-half berth.

This configuration allows the ball to quickly be transferred during the transition between lineout and maul.

Ospreys have used this set-up 12 times in the Heineken Champions Cup so far – the third-highest total – which accounts for 40% of their lineouts.

Four of their five tries in the competition so far have also begun with lineouts, including all three of their scores against Montpellier.

For their first try, Ospreys set up with four jumpers in the middle of the line: Tipuric, Rhys Davies, Adam Beard, and Roots.

Between them, these four have won 59.8% of their side’s lineouts, creating a real defensive headache for a Montpellier pack trying to identify the intended target of the throw.

The home side opt for a two-pod defensive system, whereby they set two lifting pods at the front and back of the line.

This strategy is effective in terms of blocking off zones but does leave their defence inflexible. Seeing the Montpellier loosehead prop’s closed body position, Beard springs in front of Montpellier’s rear pod – eliminating the competition.

The speed of Ospreys’ transition into the maul beats the home side, who have lost the battle of the shoulders.

The quality of the Ospreys’ maul set-up is critical. Roots and Davies powerfully propel Beard into the air, with Roots even getting on his tip toes to give his teammate an aerial advantage.

Just the right side of the law, the two lifters then exploit Beard’s twist in the air and get between the Montpellier defenders and the jumper – ensuring a quick set.

As the maul spins infield, Roots is able to drag four Montpellier jerseys out of the contest legally, allowing the Ospreys to cross the try line and stun their opponents.

Mauls are a regular sight in the modern game, but the detail, subterfuge, and skill involved to create a successful one is often underappreciated.

Combined with bravery and teamwork in the tackle, Ospreys’ maul was the smoking gun which allowed them to overpower the Montpellier pack – the platform for their three tries.

Ospreys overcoming Montpellier Hérault Rugby at the GGL Stadium is the biggest upset of the Heineken Champions Cup so far.