Is Ferrari really in the hunt at the Monaco Grand Prix?

McLaren unveil Gulf livery ahead of Monaco GP (1:56)

Daniel Ricciardo, Lando Norris, Zak Brown & Mike Jones share McLaren's limited edition livery ahead of the Monaco Grand Prix. (1:56)

MONACO -- Looking at the results from Thursday's practice session at the Monaco Grand Prix, you could be forgiven for thinking you were back in 2017.

That was the last time Ferrari looked truly competitive on F1's most famous street circuit, and the only time it has won here in the last 20 years.

But Thursday's times were genuine and a warning shot to Mercedes and Red Bull, who have dominated the 2021 season up to now.

Charles Leclerc finished Thursday's second practice with the fastest time -- a 1:11.684 -- which was 0.112s clear of teammate Carlos Sainz in second.

What's more, Leclerc set his time despite a gearbox issue limiting him to just four laps in the morning practice session.

"I was quite surprised that it ended that way because Monaco, here it' very important to do as many laps as we can," Leclerc said. "Unfortunately with the issue I had in FP1, I had done only four laps.

"I felt quite at ease with the car in FP2 and managed to put that lap [together].

"There is still a bit of margin but on the other hand, I'm sure that Red Bull and Mercedes have more margin than we have so we shouldn't get carried away too much.

"We have one day tomorrow to work hard [on setup], and let's see where we end up."

Sainz had the slight disadvantage of setting his time 10 minutes earlier in the session than Leclerc, when the track would have been marginally slower.

But to give some extra context to Ferrari's practice, Sainz also set his time seven minutes earlier than the fastest Mercedes of Lewis Hamilton and was still 0.278s faster.

Ferrari also held a monopoly on fastest sector times.

Like all F1 circuits, the Monaco lap is split into three sectors.

Sector one includes the long flat-out, uphill section from Sainte Devote to Massanet, the medium-speed left, right at Casino Square and the short blast downhill to Mirabeau.

Sector two continues down through the tightest part of the track at the Fairmont Hairpin, into the tunnel after Portier and includes the hardest braking point ahead of the Nouvelle Chicane before finishing on the exit of the high-speed Tabac.

Sector three continues through the high-speed Swimming Pool sector and includes the fiddly Rascasse and Anthony Noghes corners at the end of the lap.

Gaps between drivers tend to be smaller in sector one than the other two as the section of track is relatively fast and more time is spent at full throttle and less time is spent in the corners.

Sainz was fastest through sector one, with a marginal 0.054s advantage over Hamilton.

Had Ferrari been running a faster engine mode to achieve their fast laps, it may have been shown up by a significantly quicker first sector, yet the red cars extended their advantage in the twisty bits further round the track.

Of course, it's a possibility that Mercedes have more time to find in the first sector from running a higher engine mode, but it helps give credence to the theory that Ferrari is genuinely fast.

Sector two has the slowest corners, including the famous Fairmont Hairpin, which is the tightest corner on the F1 calendar.

Lots of time can be lost if the front of the car refuses to bite and tuck into the bend, but Leclerc looked nicely hooked up.

In sector two alone, Leclerc held a 0.396s advantage over Sainz and a 0.235s advantage over Hamilton -- a significant margin regardless of extenuating circumstances.

Running that little bit later in the session when more rubber was laid on the track may have helped, but not by a magnitude of two tenths of a second.

In sector three, Sainz regained the edge with a split time 0.128s clear of Leclerc and 0.010s clear of Hamilton.

Whichever way you look at it, and whichever part of the track you focus on, Ferrari looked fast.

However, the big question is over fuel loads and whether Ferrari was gaining an advantage by running its cars lighter than Mercedes and Red Bull.

Monaco practice sessions are all about building driver confidence ahead of qualifying, but each driver is different and not all teams will drain the car of fuel to focus on qualifying-style laps.

By comparing Friday practice lap times with qualifying times over the season, we can start to build an understanding of which teams routinely run light or heavy in practice.

The bigger the gain between practice and qualifying, the more likely it is down to fuel loads or engine modes being used to hide performance in practice.

Ferrari historically makes less of a gain relative to its competitors, suggesting it routinely runs light in practice, while Mercedes and Red Bull often find a significant amount of pace.

"It's always a bit different here, everyone runs different fuel loads, set-ups, every driver pushes differently on Thursday," Sainz said.

"Some push more, others prefer to sandbag and go more little by little. So I think there is still a lot of things to check."

But then we come back to the size of the gap -- a significant 0.390s between Leclerc and Hamilton in third.

The Monaco lap is the shortest on the calendar, meaning lap time differences between cars tend to be relatively small.

It's safe to assume the gap between the two fastest cars on Saturday won't be that big, but for context, the only time it has been this year was at the Bahrain Grand Prix, when Verstappen beat Hamilton to pole.

But as much as a race can be won on Saturday at Monaco, it is never won on Thursday.

"We definitely look close to being a genuine threat, but we need to wait, we need to wait until final practice," Sainz said.

"Things change a lot from Thursday to Saturday here, there are some drivers who sandbag a bit on Thursday, just because they want to take it easy.

"Suddenly on Saturday, Lewis always is super quick, so we will see.

"It's nice to see that we are at least closer to the front, that we are playing around at the front.

"It's encouraging for the team, there's some positive signs that the car in the corners is not that bad."

Mercedes and Red Bull now have the luxury of a full day on Friday to analyse their data, run simulations back at the factory and come up with solutions to test in final practice ahead of qualifying.

"No matter where you go, wherever you are, the car never goes, or gives you everything you want straight away," Hamilton said on Thursday evening. "You've got to acclimatise.

"There's things that even from a driver's point of view, you're not doing what you're supposed to do.

"You're experimenting, you're trying to dial your driving style in, knowing where you've got to push, where you've got to give a little bit to get some, and then you've got to work with the car.

"The car is good, I think we've made some decent steps with the balance of the car and I'm generally really happy.

"I've got some changes I need to make this evening as we analyse today and it's going to be close on Saturday."

Ferrari would love a repeat of Thursday practice on Saturday, but while it should be the Italian team's most competitive weekend in over 12 months, it's still too early to put all your money on red.

"I want to wait until Saturday [before getting excited]," Leclerc said.

"It's looking good, but for now it's looking a little bit too good to believe it.

"Let's wait and see, Saturday we will know exactly where we are in qualifying and we will go from there for the race."

The Monaco Grand Prix is live on ESPN2 at 8.55AM ET on May 23.