Has Mercedes woken from its nightmare?

The pattern of Formula 1 2017 increasingly suggests Mercedes is having real difficulty with the latest generation of Pirelli's ultra-soft tyre compound, particularly on smooth circuits that lack any real high-speed cornering challenges.

The recent Russian and Monaco Grands Prix, which both take place on such tracks, really highlighted this weakness.

OK, Valtteri Bottas winning at Sochi and qualifying within a tenth of pole at both events suggests whatever's wrong is certainly not the end of the world.

But Bottas did not enjoy an easy ride in achieving those results, and the amplified nature of team-mate Lewis Hamilton's difficulties at those tracks suggests some serious vulnerability lurks within the W08.

There is a real chance this vulnerability could be exposed again at the Canadian Grand Prix, which is also held on a smooth asphalt track, featuring a lack of high-energy, long-duration corners to load up the tyres, and again requiring use of the ultra-soft compound as the main tyre choice.

Hamilton told Autosport ahead of the Montreal weekend of how he has suffered especially when using the ultra-soft tyres, thanks to "small nuances" in the W08's set-up related to the mechanical balance and his car's brake biasing.

"The car has many strong points to it, but there is some trickiness in the way it handles and that presents us with particular challenges when we're setting the thing up," explains Mercedes technical director James Allison.

"We have a situation where we have a car with a lot of performance that is able to compete at the front, but the window in which that performance is available is quite narrow and easy to step outside of."

Mercedes brought some updates to the W08 for the Canadian Grand Prix, and also planned some set-up revisions in a bid to address the problems Hamilton and Bottas have faced on the ultra-soft tyre this season.

The team knows the pure performance lurks in the car somewhere. As Allison puts it: "the grip is there but it's ever so easy to overstep it and to pay quite a heavy penalty in lap time as a consequence".

The big test coming to Canada was to find a way to widen the W08's operating window, so that it can challenge Ferrari more consistently.

"We are going to approach [things with] a little bit different tests in practice," said Bottas on Thursday. "We have some more small update parts for the weight of the car - we are getting very close to optimum - and some things on the engine side, and some other reliability things and something to do with suspension.

"Definitely we did struggle more in Monaco, where we ran the car in a completely different way set-up wise, much softer suspension, and that way we saw more of our issues.

"Slow-speed sections, a lot of cambers, off-camber sections, the Ferrari seems to be a more stable car to drive around those type of corners.

"You can see in some tracks we struggle more and that is something we need to sort out, because we need to be good everywhere if we want to win the title."

After two free practice sessions around the Circuit Gilles Villeneuve, things are looking much better for Mercedes already.

Hamilton set the pace in the first session on Friday morning, 0.198 seconds clear of Ferrari's Sebastian Vettel. Although Vettel's team-mate Kimi Raikkonen put Ferrari on top in the afternoon, Hamilton ended the day only 0.215s behind. In Russia he was 0.709s down on Ferrari on Friday; in Monaco, more than a second adrift. So this represents decent progress.

PURE PACE RANKING

1. Ferrari (Raikkonen) 1m12.935s
2. Mercedes (Hamilton) 1m13.150s
3. Red Bull (Verstappen) 1m13.388s
4. Williams (Massa) 1m14.063s
5. McLaren (Alonso) 1m14.245s
6. Force India (Ocon) 1m14.299s
7. Toro Rosso (Kvyat) 1m14.461s
8. Haas (Grosjean) 1m14.566s
9. Renault (Hulkenberg) 1m14.604s
10. Sauber (Ericsson) 1m15.611s

"It's definitely a lot better than it was in Monaco - Monaco was a disaster," Hamilton said. "Two tenths margin is quite good in that session, so I don't know. We'll see.

"If we can improve the car overnight then I think it can be very, very close. It looks like it could be within a tenth, so it's exciting.

"It's feeling a lot more normal. There's still stuff [to do], to get these tyres working is difficult for everyone I think, [but] I didn't have a problem with the ultra-soft today."

The long runs support the impression that Mercedes is back in position to put Ferrari under serious pressure again this weekend, with Bottas averaging a lap time less than a tenth slower than Raikkonen on the ultra-soft tyre and Hamilton slightly quicker than Vettel on the super-soft.

LONG-RUN RANKING (ultra-soft)

1. Ferrari (Raikkonen) 1m16.299s (12 laps)
2. Mercedes (Bottas) 1m16.346s (7 laps)
3. Williams (Massa) 1m16.673s (12 laps)
4. Force India (Perez) 1m17.098s (11 laps)
5. Red Bull (Verstappen) 1m17.227s (5 laps)
6. Renault (Hulkenberg) 1m17.311s (7 laps)
7. Haas (Grosjean) 1m17.349s (6 laps)
8. Toro Rosso (Kvyat) 1m17.450s (6 laps)
9. Sauber (Wehrlein) 1m18.532s (7 laps)

LONG-RUN RANKING (super-soft)

1. Mercedes (Hamilton) 1m16.234s (5 laps)
2. Ferrari (Vettel) 1m16.379s (8 laps)
3. Force India (Perez) 1m16.737s (5 laps)
4. Renault (Hulkenberg) 1m17.291s (6 laps)
5. Toro Rosso (Kvyat) 1m17.656s (3 laps)
6. Williams (Stroll) 1m17.937s (7 laps)
7. Haas (Magnussen) 1m18.055s (9 laps)
8. Sauber (Ericsson) 1m18.869s (6 laps)

There is no true read on Red Bull's long-run pace, thanks to Daniel Ricciardo suffering an engine problem early on in practice two and completing no meaningful running, before Max Verstappen broke down midway through his long run on the ultra-soft, having complained he was "slow on the straights" before suffering gearbox dramas.

We also don't really know where McLaren-Honda is at, thanks to what Fernando Alonso called a "totally wasted Friday", where neither he nor team-mate Stoffel Vandoorne completed any long runs in the afternoon, and Alonso only set an eye-catching headline lap time right at the end of the session, out of sequence with the rest.

Williams and Force India both look fast here, both teams benefiting from running the latest specification of Mercedes engine, first introduced on the works cars in May's Spanish Grand Prix.

According to Force india COO Otmar Szafnauer, this update allows some of the more powerful engine modes to be used for longer in race conditions without compromising reliability.

Force India also updated its suspension ahead of the previous race in Monte Carlo, while Mercedes has made tweaks in this area too for Montreal, according to Bottas.

This is an important area of focus for many teams given the fact the Pirelli tyres are of a completely different dimension for this season, and the Mercedes cars have looked as though they've been giving up some performance relative to Ferrari in terms of compliance and traction in the early races.

From trackside, the W08 looked stronger in this area in Montreal, so perhaps those suspension tweaks Bottas mentioned are paying dividends in that regard.

Montreal is also a bit more abrasive than Sochi and Monte Carlo, which to some extent will help mitigate the tyre warm-up problems that so afflicted Mercedes in those races, and it also doesn't feature the same camber challenges as Monaco.

The bigger braking zones that feature in Montreal compared to Monte Carlo should also help generate greater loads through the front tyres, which should help with the problem of balancing out the W08's two axles that Bottas identified as a big issue for Mercedes in Monaco.

As a counterpoint, all the cars run in a much lower downforce configuration for Canada's long straights, which will hamper tyre management.

Degradation appears next to non-existent again here so far at least, but it seems as though the difference between all the compounds is such that both the super-soft and soft tyres could play a role in the race - especially if ambient and track temperatures rise.

Bottas set a competitive 1m16.446s average lap time over a five-lap run on the soft tyre, which went barely used in Monte Carlo last time out.

That's good news for Mercedes, which has done well on the soft tyre so far this season. But, as Hamilton points out: "Positioning is everything here because you can't overtake. Between the four of us it's going to be hard to overtake because we all have similar pace".

So that means extracting the most from the ultra-soft tyre will again be absolutely crucial, in order to qualify well and start the race with the advantage of superior track position.

"We need to get more out of the ultra-soft tyre," reckoned Bottas. "For me the car was feeling good on the soft, but with the ultra-soft we have more work to do with the balance and the overall grip."

So does that suggest, despite improved performance relative to Ferrari here so far, that Mercedes hasn't yet solved its ultra-soft set-up troubles?

"I wouldn't say solved," adds Hamilton. "The car is generally back to normal, but it's still a work in progress. It definitely doesn't feel like it did the last race. It's just back to normal, I would say, like it was in Barcelona."

Hamilton won that race of course, after the closest thing we've yet seen in 2017 to a proper wheel-to-wheel fight with Vettel. The Ferrari driver called his first day of running in Canada "tricky", saying he was "fighting the car" in lapping half a tenth slower than Hamilton.

Vettel is confident Saturday will be better for Ferrari, which is bad news for Hamilton and Bottas given how fast Raikkonen was.

But there can be no doubt Mercedes has taken some decent steps in the right direction with its ultra-soft set-up problems in Canada, which hopefully means F1 can get back to enjoying a full-blooded fight between four cars at the front of the grid again.