The 2021 title race is already shaping up to be a thriller with reigning world champion Hamilton and Red Bull’s Max Verstappen separated by just a single point heading into this weekend’s Portuguese Grand Prix.

Hamilton narrowly beat Verstappen to victory in the Bahrain season-opener, before the Dutchman hit back in the Emilia Romagna Grand Prix to leave the title fight finely poised after the opening two rounds.

Seven-time world champion Hamilton lost out to Verstappen at the start at Imola before being forced into a recovery drive through the field after making a rare error as he hunted down Verstappen for the lead.

Horner believes Red Bull can exploit any weaknesses Hamilton may have by putting him under extreme pressure and subsequently capitalise on any mistakes he makes.

“It has to be said that Lewis was extremely fortunate, a sentiment I’m sure he would echo,” Horner said in his latest Red Bull column.

“The red flag, which was caused by his teammate, allowed him to un-lap himself after his own accident when he would have been effectively out of the race for a podium finish.

“But it was a very strong comeback drive by him and Mercedes once again showed great race pace, so you can see there is not a lot in it at the moment.

"We will try and put as much pressure on Lewis in his title defence as we possibly can.

“He made a fundamental error when he went off which is easy to do in those conditions but after Max's victory, he still leads the championship thanks to the single point he won for setting the fastest lap in the race.

“So, if the next 21 races are as exciting as the first two, then it is going to be an epic season.”

According to Horner, the opening two races of 2021 have demonstrated that “marginal gains” will ultimately determine the destiny of this year’s world champion.

“It’s all going to be about marginal gains,” he explained. “It’s going to be about who can develop the car effectively within the budget cap.

“It’s going to be about reliability, it’s going to be about operational incremental gains, it’s going to be about human performance and it’s going to be about the drivers.

“That’s what it should be about fundamentally, the two best drivers in the sport going head-to-head.

“I certainly hope we can sustain this level of performance. Mercedes, you can see the progress they’ve made since a difficult start in the Bahrain test. They’re in good shape and they’re not standing still.

“We need to keep pushing, trying to find performance and try to make sure we have perfect weekends.”