Red Bull's Daniel Ricciardo fears Mercedes will still be impossible to beat next season - after suggesting the German car manufacturer actually extended its advantage in 2015.
Although many are predicting a tougher challenge from Ferrari next season, Ricciardo thinks that Mercedes still have plenty in hand.
"How far are they ahead? Too far," said Ricciardo, speaking at the Perth Speed Fest, where he will demonstrate the 2011-championship winning RB7 in front of his hometown fans this weekend.
"I honestly think they increased the gap this year, and obviously Ferrari caught up a little bit.
"But when [Mercedes] really wanted to turn it on, they could. They'll still be the team to beat next year and they will be hard to beat, but hopefully it doesn't go on too much longer."
Red Bull uplift
While his own Red Bull team faced difficulties this season, Ricciardo thinks the team can enjoy a brighter future now its engine plans are sorted.
"It should be better after 2015 was really not as nice as we expected," he said.
"You'd think that in 2016, we'll start to turn it around again.
"I hate the word 'expectation', but I probably set my expectations too high for this year for the start of the year, so coming into next year, I think I'll play it down."
Despite enduring a tough season, the Aussie once again praised the work of Red Bull's chassis designers.
"The chassis this year was pretty good and as we developed it, it got better and better," he said.
"If you took the straights out of the track and if the track was just made up of corners, we would have been a lot higher up."