Primoz Roglic and Egan Bernal set for showdown on hardest stage of the Tour de France

The mountains of the Massif Central may not have the same fear factor as their Pyrenean or Alpine counterparts, but the peaks peppering Friday's Stage 13 could prove unlucky for some of the yellow jersey pretenders.

Just 44 seconds separate the top seven riders ahead of the first summit finish of the second phase of the Tour – the tough double-digit western ramp of the breathtaking Puy Mary in the rugged volcanic region of Auvergne in central France.

Also known as the Pas de Peyrol, this 5.4km first-category climb cuts through old lava flows and has an average gradient of 8.1km. It's the highest road in the Massif Central and culminates with a nasty two-kilometre wall of 13% punctuated by just the single hairpin bend. Coming right after the Col de Neronne (3.8km at 9.1%) it's a beastly combo being used as a stage finish for the first time in Tour history.

A further five categorised climbs precede this stinging Monts de Cantal finale in what will be an unrelentingly undulating 191.5km for the riders. If Stage 13 features more vertical metres than any of the stages in the Pyrenees or Alps, it is also one of the most beautiful of the 107th edition of the Tour.

The opening stage of 2019 Criterium du Dauphine featured an early ascent of the southern side of the Puy Mary – past the point where Alexandre Vinokourov famously rode off the road into a tree, breaking his leg while descending in Stage 9 of the 2011 Tour de France, won by Luis Leon Sanchez the day Thomas Voeckler started his 10-day run in yellow.

Standing alongside the the huge volcano of the Plomb du Cantal, the Puy Mary was most recently used in the Tour five years later in Stage 5, won by Greg van Avermaet in the ski resort of Le Lioran. The Belgian took the yellow jersey that day in what was one of the many highlights of a 2016 season that also yielded him victories in Omloop Het Nieuwsblad, Tirreno-Adriatico, the GP de Montreal and the small matter of the Olympic road race gold medal.

Van Avermaet will possibly be on the hunt for some breakaway joy for his misfiring CCC Team this Friday – along with the likes of Julian Alaphilippe (Deceuninck-QuickStep), green jersey-seeking Peter Sagan (Bora-Hansgrohe), French duo Nans Peters and Benoit Cosnefroy (both Ag2R-La Mondiale) and Stage 12 winner Marc Hirschi, perhaps with a little help from his Belgian teammate Tiesj Benoot (Team Sunweb tend to hunt in pairs nowadays).

Swiss tyro Hirschi finally got his win on Thursday with a fine solo attack into Sarran, but the 22-year-old may now be eyeing the polka dot jersey – having drawn level with Stage 8 winner Peters, five points behind Cosnefroy. With a total of 36 KOM points on offer – the same amount leader Cosnefroy currently holds – expect this to be the subplot of a potentially enthralling stage.

But all eyes will be on the resumption of the battle for yellow after a series of stressful attritional stages since Monday's rest day. While the likes of Davide Formolo, Ilnur Zakarin, Sam Bewley, Ion Izagirre and Gregor Muhlberger have all withdrawn since the Tour hit the Atlantic coast on Tuesday, none of the big GC favourites have gone by the wayside.

In fact, the top 10 is just as it was after two stages in the Pyrenees – both of which eschewing the traditional summit finish you'd expect in the Tour. The two summit finishes so far – Stage 4 to Orcieres-Merlette and Stage 6 to Mont Aigoual – were cagey affairs with very little time gaps.

Defending champion Egan Bernal (Ineos Grenadiers) may trail Primoz Roglic (Jumbo-Visma) by 21 seconds in the general classification, but the gap has been made up entirely from bonus seconds from the Slovenian's Stage 4 win and his second place in Stage 9, plus the preceding climb of the Peyresourde.

The Colombian has kept out of trouble in the opening week, his Ineos team ever alert to the crosswind dangers while trying to nurse their mountain domestiques – Pavel Sivakov, Andrey Amador and Richard Carapaz – back to good health after their various spills in and around Nice.

Stage 13 will be a real test for both Roglic and Bernal; questions may finally be answered.

Have Roglic and his seemingly indomitable Jumbo-Visma team peaked too soon? Is he capable of getting through the seriously steep stuff? Have Ineos recovered from their early problems? Is Bernal's back injury behind him? We may soon find out…

Speaking after Thursday's longest stage of the Tour, Bernal said: "Tomorrow we will feel it in the legs. We have seen the stage when we did the recon. The last two kilometres are really steep and really hard. We need to arrive there as fresh as we can and try to do our best because for sure there will be a difference."

But it's much more than a two-horse race, with Frenchmen Guillaume Martin (Cofidis) and Romain Bardet (Ag2R-La Mondiale) 28 and 30 seconds down, and Nairo Quintana (Arkea-Samsic) completing the top five at 32 seconds back alongside compatriot Rigoberto Uran (EF Pro Cycling).

The mercurial Bardet is the local rider on Friday, hailing as he does from the nearby town of Brioude. Bardet was not meant to be riding this year's Tour but the Covid shake-up saw him switch his target from the Giro back to the race in which he came second in 2016.

With the GC hopes of last year's French darlings Thibaut Pinot (Groupama-FDJ) and Alaphilippe falling by the wayside, Bardet and the 27-year-old Martin are flying the tricolore for the French. So far they have managed to pass under the radar, but Friday's whopping 4,400 metres of climbing will be a proper test of their GC credentials.

With Slovenia's Tadej Pogacar (UAE Team Emirates), Britain's Adam Yates (Mitchelton-Scott), Colombia's Miguel Angel Lopez (Astana) and Spain's Mikel Landa (Bahrain-McLaren) all in the top 10 and within 1'42" of the race summit, we can expect an explosive day amid the volcanoes of the Auvergne.