Two days on from a Valencian Grand Prix flameout (two riders in crashes, one more out of the top 10, one more not even taking part) and the farewell of a legend rider, the vibes at Honda underwent a major course correction.
And the culprit behind that course correction was an extremely assured debut of the new Honda RC213V prototype, which after a year of mostly-misery suddenly promised real, tangible progress for the first time in a long time.
The headline result through the seven-hour Tuesday test was new signing Luca Marini, brought in on a two-year deal as a replacement for the outgoing Marquez, placing in the top 10.
Marini was still seven tenths off pace-setter Maverick Vinales, and the run did look like a 'time attack', so the gap wouldn't be very good for an actual race weekend.
For a first day on a Honda, though, a bike that's supposed to be much less friendly and easy to understand than the Ducatis Marini has been riding all his MotoGP career? Very good.
To be just half a tenth off his own best time from the Valencian GP weekend? Very, very good.
Marini wasn't free to speak to media - seemingly for the ever-familiar contractual reasons - and neither was fellow Honda-to-Ducati traveller Johann Zarco.
But feedback from those who had just gone through the miserable 2023 campaign made it clear - if Marini's laptime piqued your interest, you're not wrong to take it as a good sign.
A midday MotoGP.com interview with (potentially on-the-way-out) team manager Alberto Puig was about as effusive as you'd expect the guarded and matter-of-fact Spaniard to be.
"It looks like the feeling, the general feeling of the bike, is quite different," he said.
"Different in a good way. Because sometimes things are different - but different bad or different good? Today was different good."
LCR Honda team owner Lucio Cecchinello suggested to MotoGP.com that there was solid evidence of Honda going "in the right direction" too, based on the rider feedback he'd heard.
When told by The Race right before the start of a media session that Puig seemed quite happy, rider Joan Mir let out a jovial "f***ing hell", referencing Puig's usual unflappable demeanour.
But in doing so Mir also immediately set the tone for a media debrief that was perhaps the most outwardly excitable of all the ones held - rivalled only by rookie Pedro Acosta.
A wide-eyed Mir, who had sat out the Valencia race weekend after yet another crash with painful consequences on Friday, was almost bewildered by how much he had enjoyed the bike.
"Honestly, I'm very happy. I'm very happy. It's the first time I'm able to feel a difference since I arrived," he raved.
"That something really works, works better. The result, the laptimes are there. I could make a good pace, every exit I was able to be strong, during all the day."
The grip - "something we complained about all year" - seemed to take a step forward. But also, the bike was bigger, yet lighter.
"That helps a little bit also on the turning side, to stop. Everything a lighter bike can help with," Mir added.
"So that is just an advantage. And then, honestly, in the morning I was worried because with all this wind sometimes it's different to try and make a proper comparison but even with this wind straight away I was able to feel an improvement.
"And that is honestly very good.
"The last exit also was pretty good with the used tyre all the time, being with that [1m]30[s]-lows, that is something that makes me happy, because it's the laptime that you have to do to be in front.
"So, it's fantastic."
Mir was only 13th-fastest, but said he never tried a time attack run and stressed he and Honda "had to be happy" with the laptimes.
There's still "margin" coming into the Sepang test, as Mir wants to work on the engine character more, to be able to rely less on electronics and have more torque control in order to confer a late-race advantage.
But it sounds like "some steps" were already made there. And as for the incessant crashes of 2023, the bike apparently offers "a better feedback on the front" to the rider.
"It's only the first test - but it's true that this track, you request a lot of the front," Mir offered.
It was overall described by Mir as "a reaction", something he had been desperate for for much of the season.
He was less unimpressed than Marquez by what Honda had brought as a 2024 prototype to the mid-season test at Misano two and a half months ago, but this was clearly a different league.
LCR Honda rider Takaaki Nakagami said his time on the bike had been very limited because the prototypes were instead being used by Mir, Marini and Zarco.
This in itself is somewhat telling, as normally, if the step between two bikes is on the lesser side, new arrivals are usually given the older, better-known version to bed themselves in and adapt.
But with Nakagami having to wait, he was held up further by the sole Honda crash of the day - a small tip-off from Zarco. He was supposed to take over the bike of his LCR team-mate but needed to wait for repairs.
"But the first impression was pretty good. I mean the engine character and the edge grip was improving," said Nakagami.
"The riding position is really uncomfortable [for me] on the braking [because it was tailored for Zarco].
"I didn't want to make any stupid mistakes in the last few minutes. Just [get] the taste of the bike. Also the bike is very light and the agility is much better and the engine performance I like.
"The impression was good. I can feel some potential."
We have seen a new Honda make an ultra-promising debut not that long ago and then turn out to be lacking over the rest of the season - see the 2022-spec RC213V in the Qatar test, in the Qatar race and then over the rest of the season.
So, even if there's an existing comparison with the Valencia weekend days prior that had been decent but not overwhelmingly so, is it possible that this is a false dawn? Absolutely.
But it's a real, tangible sign of progress, and it will give everyone in the project a feeling to hold on to as they go into what otherwise threatened to be a pretty gloomy winter break - if anyone has enough energy to be gloomy anyway.
This is, ultimately, the case for Tuesday having been the best day of Honda's 2023.
Honda, though it finished last in the manufacturers' standings, didn't have a total write-off of a season.
Alex Rins won for LCR at COTA, which didn't really prove a lot about the bike ('Honda wins at COTA' isn't a rarity) but did suggest Honda had secured a great signing before Rins got injured and then committed to Yamaha.
Elsewhere, there were some Marquez heroics and a glimpse or two from Mir. And alongside Tuesday another contender for Honda's best day was Monday - when the new concession framework was announced, giving Honda a lot more freedom in terms of testing for 2024 - more tyres, the ability to test with factory riders, an extra aero homologation and no engine freeze.
But this had been in the works and a virtual guarantee to arrive for a long time. And there was no certainty that concessions was something Honda would be able to make effective use of.
Tuesday was much punchier. There are still no guarantees - but there is, all of a sudden, a potential new dawn and a programme rebuild that looks to have accelerated itself substantially.