Ahead of the Portuguese Grand Prix, we take a look at some of the main questions arising from the 2021 season so far...
Who has the fastest car?
Ahead of the third race weekend of the season, it's hard to pick which team is the favourite for victory.
Mercedes will likely claim Red Bull is the favourite and vice-a-versa as they look to shift the pressure from one to the other, but from the evidence of the first two races it is too close to call.
That's the way Formula One should be. It's far more exciting to have two (or more) teams fighting for victory than the near certainty of one team dominating over the course of the year.
At the two races of 2021, it seemed as though Red Bull had the faster car, but it was also clear that the margins were incredibly small.
Verstappen was 0.4s clear of the fastest Mercedes in Bahrain qualifying and would have been up to 0.3s clear had he not made mistakes on his Imola qualifying lap.
But Mercedes emerged as race winners in Bahrain and Hamilton was putting pressure on Verstappen before spinning in Imola.
Speaking after the Emilia Romagna Grand Prix, Mercedes' trackside engineering director Andrew Shovlin said: "We are not going to walk away from this patting ourselves on the back, saying that we might have had the faster car by a small amount.
"We are walking away from here saying, we are not good enough and they will win the championship if we don't improve our car very quickly.
"That is our mindset, that we are still the ones chasing."
It's clear that the track layout and weather conditions will play a role in who has the fastest car at race weekends this year, and Portimao is different enough from both Bahrain and Imola for the tables to turn again this weekend.
One thing that has become clear in the first two races is that individual driver errors or exceptional performances can, and will, make the difference.
What's happened to the form of the drivers who changed teams?
It's early in the season, but there's one definite trend you can see from the first two races. The drivers in new situations are not quite at the level you'd expect.
The four drivers who swapped teams, Sebastian Vettel, Daniel Ricciardo, Sergio Perez and Carlos Sainz, and one driver who returned to F1, Fernando Alonso, have all made mistakes and/or failed to match the pace of their new teammates.
Vettel's been pretty underwhelming since joining Aston Martin. Ricciardo's been off the pace and even had to let teammate Lando Norris through at Imola -- Norris has been the star of the midfield so far. Perez has been inconsistent, qualifying second at Imola and then turning in a very uncharacteristically sloppy performance the following day. Sainz has a tough benchmark in Leclerc and has said he's not at the level he wants to be at quite yet, while Alonso looked fairly unspectacular throughout the Emilia Romagna Grand Prix.
It's early days, of course, but a lot was expected of these drivers. The fact so many good drivers are struggling goes to show you how difficult it is for a driver just to switch teams and immediately drive to the limit from the beginning.
Some of the drivers in that list might simply have met their match in a new environment, but each can take comfort in the fact that they are not alone in struggling to adapt quickly.
There's lots of things which would explain these slow starts. Modern F1 cars are complicated beasts and track time is key to getting up to speed quickly. This is a massive issue for these drivers - preseason was just three days this year, down from six in 2020. That's also a misleading way of putting it, because it was effectively three eight-hour days split between two drivers.
These drivers have made the switch at a time when cars are more or less an evolution of last year's cars, meaning their teammates are likely far more comfortable than if they were joining a team with a completely new concept. Ricciardo also took a while to get up to speed when he joined Renault in 2019. While supreme on the brakes at Red Bull, learning how to get the most from the Renault, which also had less downforce, was not simply the work of a moment.
"I'm not naïve to know that a new team is a new challenge," Ricciardo said at Imola. "I'd say I'd thought the transition would have been quicker, but then it's race two so I don't want to be like, 'I was expecting to be on the podium already'."
He added: "Obviously the reference to Lando is a strong one, so I'll just chip away and do better."
Alonso might have been away from F1 for two years but such is his reputation that few expected anything other than the best as soon as he returned. To his credit, he refused to use the time out of the car as an excuse.
"I think each of us has a different story and a different theme or difficulty," Alonso said. "I changed teams many times -- I even changed categories or series many times -- and there is always a period of adaptation.
"But it has never been an excuse, and it's not been an excuse now. I should be better. I was not at the right level this weekend, but I will be in Portimao."
Red Bull boss Christian Horner gave Perez a ringing endorsement despite his error-filled second race with the team.
"It's different to what he's used to," he said. "He did a mega job to put it on the front row, only just missed out on that pole position.
"There's great races to come from him in the future. We could see in clean air his pace was strong."
All of those drivers deserve the benefit of the doubt at this stage in the season, given the limited amount of time they've had to adapt to a new scenario.
But the clock is ticking and, with three races over the next four weeks, the pressure will really start to mount if they're still struggling by the end of May and the Monaco Grand Prix.
Are Bottas and Perez destined to be wingmen in 2021?
As impressive as the battle between Hamilton and Verstappen has been, it has also highlighted a gap in performance to their teammates.
After two rounds, Valtteri Bottas is already 28 points behind championship leader Hamilton in the standings and Perez is 34 points adrift. There is plenty of time to narrow those gaps over the remaining 21 races, but if they grow further by mid-season it will be hard to imagine either driver getting back into title contention.
Bottas' performance in Bahrain was on a similar level to those of Hamilton and Verstappen, but he was let down by a slow second pit stop. It's very unlikely he would have come out on top in that battle, but in terms of pure pace he wasn't far off.
Yet in Imola, Bottas clearly struggled. He qualified eighth on the grid and then spent the majority of the race stuck in midfield traffic that he really should have been able to overtake.
The lack of performance in the race was one of the contributing factors behind his collision with George Russell, as he should never have been in a position where his Mercedes was at risk of tangling with a Williams.
Both the poor qualifying performance and his lack of pace just before the accident were blamed on a lack of tyre temperature, which left him struggling for grip at crucial points over the weekend.
Bottas struggled in similar circumstances at last year's Turkish Grand Prix, and it seems as though it is among his weaknesses compared to teammate Hamilton, who won in Turkey and finished second in Imola.
"For me personally, for example compared to Lewis, tyre temperature was so on a knife-edge in qualifying, that sometimes you get it to work, like me in Q1, when I did a much faster time than in Q3, I got them to work," Bottas said in Imola. "Then for some reason I couldn't get them to work in Q3 the same way.
"It's all about one or two degrees of surface or tyre temperature. It's hard to explain. Obviously track temp was changing a bit, depending how much cloud there was etc, so maybe that had a bit of a factor."
In warmer conditions at upcoming races, Bottas might be able to claw his way back into the title fight, but he already needs Hamilton and Verstappen to experience a bad weekend to get back on level terms.
As mentioned above, Perez has swapped teams over the winter and he has admitted he is still adapting to his new Red Bull.
His strong performance from the back of the grid in Bahrain and his second place qualifying performance at Imola hints at his potential when he get things right, but there have already been several uncharacteristic mistakes in the first two races.
By his own admission he messed up at Imola, including receiving a penalty for attempting to regain positions under the safety car after spinning out -- a rule he should not have fallen foul of.
But even if we cut Perez some slack, it's hard to imagine him taking the fight to Verstappen week-in, week-out.
"I have a good reference in Max, he is just getting 100% all the time out of the car, and I am just adapting myself to it," Perez said in Imola after qualifying. "Learning, step by step, I wasn't expecting myself to be here [second on the grid] at the moment as I feel I am miles away from where I should be.
"Things are not coming naturally yet -- so [qualifying second] was a good boost in confidence."
With the title battle set to be incredibly close between Hamilton and Verstappen, Perez and Bottas could find themselves shifted into support roles if their results do not improve.
If they remain over 25 points off the lead of the championship by the mid point of the season, Mercedes and Red Bull could end up calling on them to sacrifice their own strategies -- or even track position -- to help their teammates.
Also of interest...
Has Russell damaged his ties with Mercedes?
Russell's clash with Bottas was one of the main talking points from the race in Imola as a Mercedes junior driver tangled with a Mercedes race driver and took both out of the race.
The fact the two drivers are fighting for the same seat at Mercedes next year adds extra spice to the story, and it was interesting that Mercedes team boss Toto Wolff held both drivers to account for different reasons.
But one accident on a damp track is unlikely to impact the long-term futures of the two drivers.
Russell issued an apology to Bottas the following day, which suggests the air was cleared behind closed doors, and the Williams driver will be keen to remind everyone why he was so highly rated by Mercedes in the first place at the upcoming rounds.
Unless Bottas continues to struggle for performance, it's unlikely the two will be sharing the same section of track in the near future, so a couple of clean races and all will be forgotten.
Has Tsunoda been over-hyped?
After winning a legion of fans with his heroics at the opening round in Bahrain, AlphaTauri rookie Yuki Tsunoda made a series of mistakes over the Imola race weekend that left him last on the grid and 12th in the race.
The mistakes were a reminder that Tsunoda is very much a rookie, but they should not detract from the flashes of pace he has shown in his short F1 career.
Like all rookies, he'll make mistakes and needs time to learn from them. At this stage, it's too early to judge him either way.
Will Aston Martin follow through on its criticism of the 2021 rules?
After making headlines early in the Imola weekend by calling for a change in this year's aero rules, Aston Martin toned down its messaging on the issue by Sunday evening.
It's seems clear that aerodynamic rule changes over the winter have impacted some cars more than others, but the debate has now shifted to whether the rules were changed with the intention to peg Mercedes and Aston Martin back or -- as the FIA claims -- to help avoid tyre failures like the ones at Silverstone last year.
On Sunday evening in Imola, Aston Martin team principal Otmar Szafnauer said: "We've had a couple of meetings with the FIA and I think at this point, we're pretty satisfied that all the correct steps were followed.
"We're still in discussions, we're just trying to discover what all the steps were to make sure that it was done properly and equitably. So that's the reason for the discussion."
No further communication on the issue has followed in the gap between races.