Jenson Button feels Ferrari's progress last winter is evidence as to what Honda can achieve before the start of the 2016 Formula 1 season.
Ferrari scored two podium finishes in a poor initial campaign with the 1.6-litre V6 turbocharged hybrid power unit in 2014.
But it emerged as the closest challenger to Mercedes last season, winning three races with Sebastian Vettel and almost doubled its points tally compared to the previous year.
While Honda's return to F1 this year was shocking given the lack of reliability and power of its engine, Button feels Ferrari has at least shown there is a way forward.
"It was great to see them [Ferrari] pick up the pace," said Button, who finished 16th in the points with a best result of sixth.
"I heard rumours they found a hundred horsepower over the winter. I don't know if that's true or not.
"But whatever they found, it was massive and they took the fight to Mercedes on many occasions. It was good to see.
"Obviously we need to make even bigger steps if we want to achieve that, but it can be done over a winter."
Button has also dismissed the prospect of operational difficulties over the winter holding back McLaren-Honda as a partnership.
Comments were aired throughout the season that suggested the Japanese culture, and the company's methodical way of working, would prove a hindrance to McLaren.
Button said: "I think there are always issues on both sides, but I don't think Honda get blamed for everything, I don't think that at all.
"We had a lot of issues this year. We've got to resolve them as quick as possible because next season is not far away.
"It's going to be a long, hard winter for us, but an exciting one as well, as there is a lot coming."