Ferrari racer Sebastian Vettel has said that it will be "very difficult to turn things around" with the form that Mercedes has had for the last 15 races or 14 races.

After unexpectedly winning the Singapore Grand Prix last Sunday, Vettel mentioned the bitter truth about Ferrari's current scenario in F1. 

"I've been around for a while now with Ferrari and I think there's only one way for Ferrari to be back, which is when we win the championship. That's a very harsh judgment but that's what it is, that's the reality," Vettel told motorsport.com. 

The first half of 2019 was a forgetful phase for Ferrari because of a series of near-misses that handed Mercedes an invincible advantage. However, by claiming three victories in the last three races -- Belgium, Italy and Singapore -- Ferrari have received a new life ahead of the 2020 season. 

Ferrari's young racer, Charles Leclerc, who bagged the wins in Belgium and Italy, is a total of 96 points behind the championship leader, Lewis Hamilton. Vettel, on the other hand, stands fifth on the table with 194 points, with just six more races remaining in the ongoing season. 

Meanwhile, numerous errors from Vettel, Leclerc and the team throughout the season so far have given their arch-rivals Mercedes a good 133-point lead in the constructors' championship. 

Accepting that Ferrari are not the best team at present, Vettel said, "We're working very hard on that. I think this year will be very, very difficult to turn things around with the current form that Mercedes has for the last 15 races or 14 races. We keep fighting because anything we learn this year will help us next year."

"But we need more. We want to be the best team, which currently we are not. The last races have been good for us, so that's great for our self-confidence inside the team and for everyone, but there's still a lot of work ahead of us," he said.

The upcoming race weekend is in Russia and Mercedes are the most successful team there. Since Sochi's return to F1 in 2014, Mercedes have won in every single year. Out of the last five races in Russia, Hamilton has won three and the other two wins have gone to Nico Rosberg and Valtteri Bottas. 

Ferrari are once again not expected to be fierce in the upcoming Russian Grand Prix and hence the race will be a major test to check if their latest upgrades have put the side on par with the likes of Mercedes and Red Bull or not.