Lewis Hamilton believes he faces the toughest title fight of his Formula One career in squaring up to Mercedes team-mate Nico Rosberg this season.
Hamilton heads into this weekend's Monaco Grand Prix, a race he wants to win more than any other this year, at the top of his game after a run of four successive victories.
Despite such domination, Hamilton only has a three-point cushion to Rosberg after a mechanical failure in Australia brought his season-opening race to a premature end.
It means every point is precious and every shred of detail vital if the 29-year-old Briton is to win his second world championship.
But with his main rival for the crown in the opposing garage and with the duo sharing all the data, it means there is little opportunity to gain the upper hand.
Asked whether this was the toughest scrap he had encountered in F1, Hamilton said: "Definitely, I would say so.
"It's the same for Nico because I see his data, which makes it so hard for either of us to get any advantage at all.
"It would almost make sense to copy his set up. You could if you wanted to, just do exactly the same, and then it would just depend on ability.
Spanish Grand Prix - In pictures
Spanish Grand Prix - In pictures
1/10 Sunday race
Lewis Hamilton celebrates with his trophy after winning the Spanish Grand Prix
Nico Rosberg attempts to hunt down his Mercedes team-mate in the battle for Spanish Grand Prix glory
3/10 Saturday final practice
Spanish hero Fernando Alonso prepares to head out where he will receive the usual ferocious support he has grown used to in Barcelona
4/10 Saturday final practice
Nico Rosberg finished fastest in final practice for the Spanish Grand Prix ahead of Lewis Hamilton
5/10 Saturday final practice
Williams' Felipe Massa walks through the pit-lane ahead of qualifying
6/10 Friday second practice
Esteban Gutierrez negotiates the sweeping turns 1 and 2 in his Sauber
7/10 Friday second practice
Daniel Ricciardo enjoyed a far more successful practice session as he ran behind the Mercedes pair in third position
8/10 Friday first practice
A concerned Sebastian Vettel keeps guard over his broken down Red Bull as he looks on with a fire extinguisher at the ready
9/10 Friday first practice
Sebastian Vettel pushes his Red Bull after it grinds to a halt on the Catalunya track
10/10 Friday first practice
Lewis Hamilton leads the first practice at the Spanish Grand Prix
"But I'm pretty sure we'll keep sharing data. That's how it works in all the teams. At McLaren it was the same.
"So that will continue, which means you've always got to keep working at getting your set-up right.
"We saw that in the last race in Spain. If you are just off, as I was, and the other guy gets it right, you see the balance changes between the drivers. That's what I've got to work on.
"Overall, though, this team has the potential to be the best. In fact we are already there, but we can't take it for granted - we've got to keep working and improving, which we will do."
In winning all five races to date, there is talk of Mercedes sweeping the board for the first time in the sport's history.
McLaren came close in 1988 when Ayrton Senna and Alain Prost won 15 of the 16 grands prix that season.
Hamilton, though, is refusing to contemplate the prospect of Mercedes winning all 19 races this year.
"I obviously wasn't watching back in '88, but what McLaren did is a quite incredible achievement," said Hamilton.
"After watching Ferrari's dominance (from 1999-2004) and Red Bull's dominance the last four years, which has been painful, for us to have a 48-second gap (as was the case in Spain) is quite unreal.
"But I'll never sit and say we'll win all the races because I know there are going to be difficult races we're not going to be happy with.
"Reliability is going to become a player, as it was for me in the first race, so I never want to jump the gun.
"Naturally, if the team did achieve that then it would be absolutely unreal."
Although Rosberg won last year's Monaco Grand Prix from pole, there is some suggestion Mercedes may not have it all their own way this Sunday.
With the tight, twisty streets more appropriate for cars with high downforce than outright speed, it is believed Red Bull will put up more of a fight.
"We're still going to be quick there," said Hamilton.
"But things should close up as there are not really many straights, so hopefully we'll see a much closer race.
"Red Bull have a very good downforce package and McLaren should be good there as well.
"But after the last few races, which have been just incredible and I honestly never expected I'd win four consecutive grands prix in my career, I'd love for that run to continue this weekend."