He added to that comment by evaluating where his Mercedes team sit in the scheme of things.
"We are not the quickest at the moment," he claimed. "Ferrari look quickest, then perhaps Red Bull and maybe McLaren. But we are currently not at the top. At the moment, I don't think we will be competing for wins."
The third, and final day of testing did little to change Hamilton's view, except it was Max Verstappen in the Red Bull, rather than a Ferrari, that set the fastest time, and by a considerable margin, being 7/10s of a second quicker than the Ferrari of Charles Leclerc, with Fernando Alonso in the Alpine third quickest.
George Russell in the Mercedes was fourth, over 1 second slower than Verstappen, and he like Hamilton, has cast doubt on the pace of the Mercedes.
"We're trying to get every last bit of performance out of it and just trying to test those limits," Russell commented.
"But it's bouncing around a lot. From within, it's not the comfiest of at all, honestly, but I don't really care about comfort if the performance is there. At the moment, the performance isn't there - we do seem to be a step behind our rivals.
"We have a lot of work do between now and [the first race] next week to understand the issues because, in every condition, the Red Bull and Ferrari seem a step ahead of us."
Hamilton seems to agree with his teammate.
"Next week we will get a much better showing of our pace, but I think people will be surprised maybe," Hamilton teased. "Or at least people keep talking about us, talking themselves down.
"I think we have bigger challenges this time and they are not one-week turnarounds. I think they will take a bit longer. But from what I'm told we have a significant amount of pace to find."
Ferrari driver Carlos Sainz has stated he does not buy into the pessimism coming from Russell and Hamilton.
"I think it's typical Mercedes, typical George," he said.
"Just hype up the others and then come to the first race and blow the competition away, which is typical. They have done it for five or six years now and they keep [performing] in the first race.
"So, as you can imagine I don't think much [of the comments] and yes, already in GPS [data] we can also see what they are doing and yes, I'm not going to say much."
Point taken, because prior to the first grand prix in 2019, Hamilton said the gap between Ferrari and Mercedes was "potentially half a second, something like that. But we will be analysing a lot from this test [Barcelona] and there will be some mods that we'll try and implement before [Australia].
"There's obviously not a lot of time, but over the next week, hopefully we'll gain another tenth at least just in our understanding of the car."
It's history now that Valtteri Bottas in the Mercedes won the 2019 season opener in Australia, with Hamilton second.
The latter then won six of the next seven races, with the other one going to Bottas. It would not be until races 13 and 14 that Leclerc would win two races for Ferrari. He would end up fourth in a championship that Hamilton easily took with 11 race victories, with Bottas a distant second and Verstappen third.
Is Mercedes "sandbagging" again this year? Perhaps not, according to Alpha Tauri driver Pierre Gasly, who 'raced' with Hamilton during testing.
"I was kind of surprised to battle with Lewis," Gasly, who was ninth in last year's championship, said.
"I think the conclusion is Mercedes probably doesn't look as good as they were in the past."
Gasly says his car is an improvement on last year's car.
"It was clearly better. We overtook each other a couple of times, stayed close to each other. It was definitely an improvement so I think racing should be quite fun this year."
"I just don't know where we stand in the midfield at the moment. We know we won't be going for the championship this season," he added.
Like Sainz, Verstappen does not buy into the Mercedes drivers' claim that they are off the pace.
"If someone is doing well or a team that everyone expects to do well, then it's; 'Oh no, we're definitely not the favourite'," Verstappen observed. "And then a week later, when things do go well, all of a sudden it's: 'Oh no, but we turned it around completely within a week. Not normal, unbelievable work. Thanks to all the people in the factory!'
"And they were still very strong during the first race weekend [of 2021] after a similarly low-key testing performance," he sarcastically added.
Alonso thinks there will be major swings in momentum throughout the season as teams introduce further upgrades.
"I think it's going to be a long game, that is for sure," he told Motorsport.com.
"The rate of development is going to be huge, and there are 22 races. I remember here last year I retired the car and Esteban [Ocon] was P12 or P13, so zero points after Bahrain. And then we won a race in Hungary, and we were enjoying the season from then on, so I think this year is going to be a long game to play and I am confident we will have a good season."
The same sentiment might not apply to McLaren. Daniel Riccardo missed the test due to Covid, leaving Lando Norris to test the car, the performance of which team principal Andreas Seidl was "not fully happy" with due to a problem of overheating brakes.
"The plan definitely didn't go to plan," Seidl said. "We had an unexpected problem on the front axle with the brakes which limited our running quite a bit. It definitely put us on the back foot."
The biggest improver in testing was Haas, who have recalled former driver Kevin Magnussen to replace Russian driver Nikita Mazepin, who the team sacked due to Russia invading Ukraine. His father's company Uralkali, the naming sponsor, is also gone, which will likely end up in a court battle, as Mazepin Senior wants his money back.
Haas driver Mick Schumacher set the eighth quickest time in testing, ahead of his mentor Sebastian Vettel in the seemingly improved Aston Martin.
So, with Verstappen quickest, will the new world champion get off to a winning start in Bahrain? Red Bull team boss Christian Horner is not that optimistic.
"For me, the car that looks the most settled on circuit is the Ferrari at the moment," he said. "They have had a very strong testing period so far both in Barcelona and Bahrain. I would say they have looked extremely competitive on track.
"The rate of development will be fast and intense and I expect that to change and Mercedes will be a huge factor in this championship, I have no doubt.
"I think what we can say is it will only be next Saturday you will get the first snapshot when the fuel comes out, people run as close to the weight limit as they can and we will see how competitive they are."
Ferrari boss Mattia Binotto has downplayed his team's favouritism.
"I heard someone saying we're the favourites," he said. "The others are the favourites, they are the world champions, who with the Drivers', who with the Constructors'. They had such an advantage last year which proves how strong they are as a team too."
We will all be wiser come the early hours on Monday.