It's lap 43 of 50 during the Saudi Arabian Grand Prix, and Charles Leclerc and Max Verstappen are battling for the lead.

The pair are approaching the final turn before heading down the main straight when they both brake so hard they almost come to a stop.

Why? Because neither driver wanted to be in first place.

The first two races of the Formula 1 season have delivered the wheel-to-wheel battles fans were promised in the off-season.

But the new regulations which have provided entertaining racing have had a surprising consequence — the Drag Reduction System (DRS) now works too well.

The DRS has been a force for good since being introduced in 2011 but some are now calling for a rethink to stop drivers from actively avoiding the lead of the race.

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What is DRS and why was it introduced?

DRS is a mechanism on a Formula 1 car where a driver can push a button on the steering wheel to open the car's rear wing, reducing drag and allowing the car to go faster.

But DRS can only be activated if a driver is within one second of the car in front, and in a designated zone of the track.

It was introduced to combat the problem of F1 cars not being able to overtake, which was leading to boring racing.

The aerodynamics of the cars had become so complex that the hot, turbulent air left in a car's wake made it impossible for another to follow without losing performance and having its tyres overheat.

So, DRS was introduced to give trailing cars some extra speed to try and pass.

Why is it a problem now?

F1 has undertaken one of the largest regulation changes in the sport's history.

New rules governing aerodynamics, as well as larger wheels, have been introduced to allow cars to follow each other closely.

The new rules have worked, with the opening two races of the season producing great wheel-to-wheel racing.

But now that cars can follow more closely, the DRS has become a weapon, not an equaliser.

In both Bahrain and Saudi Arabia, Charles Leclerc and Max Verstappen were tactical in their use of DRS.

Both circuits have two DRS zones, within a few corners of each other.

Leclerc and Verstappen would try to be in second at the end of the first DRS zone, so they could open their rear wing just a few corners later and breeze past, into the lead.

It led to the almost comical moment when both drivers, fighting for the lead, nearly stopped on track in a bid to be behind.

So what should F1 do about this?

Potentially nothing.

If there is one positive about powerful DRS, it is that it has made drivers be very calculating in how they race.

That's something Jenson Button, the 2009 world champion, said he had enjoyed from the first two races.

"It's such good racing," he said on the UK's Sky Sports F1.

"It's nice that it's not just about pure speed.

"It's a real thinking man's game.

"Maybe it's not the purest form of racing, but I like the strategy involved."

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But not everyone is as excited as Button.

Red Bull boss Christian Horner is calling for F1 to examine where the DRS zones are located, to avoid situations like the one in Saudi Arabia.

"The DRS is so powerful you could see that there was a game of cat and mouse going on between the drivers," Horner told motorsport.com.

"I think maybe we should look at where that DRS detection zone is for future years. You definitely want to avoid being in that situation."

DRS battle continues with four zones in Melbourne

Sunday's Australian Grand Prix around Melbourne's Albert Park circuit looks set to bring more DRS battles, with four zones designed for close racing. 

Like Bahrain and Saudi Arabia, there are DRS zones within a few corners of each other, potentially leading to drivers wanting to hold back so they can be the last to open their rear wing. 

After the DRS zone down the main straight, drivers have just turns 1 and 2 before the next zone to potentially have the speed advantage. 

Later in the lap, drivers can potentially use DRS between turns 8 and 9, and between turns 10 and 11. 

If the first two races are an indicator, the "cat and mouse" game between drivers will be played again on Australian soil this Sunday.