Abu Dhabi, Dec 11 (IANS): The 2021 Formula 1 Championships is going to the wire with contenders in both Constructors and Drivers' Championships going neck and neck with Vax Verstappen of Red Bull and Lewis Hamilton of Mercedes tied on 369.5 points each with Mercedes leading Red Bull by just 28 points in the constructors' title.

After 21 Grands Prix races, it all comes down to Saturd'y's top-10 shootout and Sund'y's season-ending Abu Dhabi race. With Hamilton topping the second free practice, Red Bu'l's championship contender Max Verstappen -- and Team Principal Christian Horner - have admitted that they have their work cut out to catch Mercedes following Friday's running at Yas Marina.

Defending champion Hamilton set the pace in second free practice after finishing third to teammate Valtteri Bottas and leader Verstappen in first practice, while Verstappen took fourth in the second session. That result led the Dutchman to say that things 'idn't go quite to plan at Yas Marina Circuit on Friday.

"I mean, we're still learning and understanding a few things but of course clearly the short ru' didn't go to plan - lacking a bit of pace - but the long runs were quite a bit more competitive so of course' that's also a bit more important," he said.

Team boss Horner added that Mercedes have the edge on this circuit, as they are outpacing Red Bull in Sectors 1 and 2, said a report on the Formula1 website "They [Mercedes] look very competitive here, certainly in the first two sectors. I think Sector 3 we come back at them, but the damage is done in the first two sectors. We've still got 24 hours or 23 hours [before qualifying] to try and find a better set-up and a bit more pace.

"We've got plenty of data, we've got some areas of the car we need to tidy up "vernight," added Horner. "It's going to be a long evening certainly here, back in Milton Keynes, trying to tidy up the car. I think the long-run pace looked sensible; we just need to tidy up the pace for the short runs."

But the Team Principal explained that changes to the circuit at Turn 5, Turn 9, and in the final sector have possibly changed this race into a two-stopper - which Red Bull may have anticipated as Verstappen used soft tyres for his race simulation in second free practice, said the report.'

"I think it's on the cusp [of being a two-stop race]," he said. "I think now with the change to the circuit layout here, I think tire wear is going to be a real factor, particularly the long left-hander [Turn 9] puts a lot of energy into t'e tyres. So it's sort of 50/50 when you look at it. So, it's going to be fascinating to see which strategy prevails."

As for their second driver Sergio Perez, he reiterated that Red Bull will have to work har" and choo"e the "best bits" from a day that saw them trail Merce'es.

"I think we've got some work to do overnight. We tried very different set-ups across the cars, so I think we've got plenty of information that we have to go into detail through and pick out the best bits," said the Mexican.

Red Bull have a 28-point deficit to Mercedes in the constructors' championship, which on Friday Horner"admitted "ould be a "long shot" for them to clinch this weekend -- but Verstappen and Hamilton are equal on points at Yas Marina.