Carlos Sainz Jr thinks a "good surprise" from McLaren engine supplier Renault could help his team make a "big step" this year.
Renault has talked up the progress it has made with its 2019 engine, with the company's F1 managing director Cyril Abiteboul saying it had found "significant" power gains over the winter.
"Everyone looks to be talking very nicely about that engine," said Sainz at the launch of the 2019 McLaren on Thursday.
"I really hope it is what they are talking about, and we have a good surprise in testing and we have those horsepower.
"Last year, as a Renault driver, we would've needed those horsepower to beat Haas more regularly.
"So hopefully it comes, because it would be already a very big step for for McLaren.
"It would be a step for free that would put us already in a much more comfortable place."
Although McLaren is coming off the back of a challenging 2018 campaign, Sainz thinks its situation is much improved this year - and says the fact the team has hit its build schedule is a clear sign of things being better.
"The team has done their homework nicely," he explained. "You've seen the car ready here, five days before testing, and that's a good sign because it means the car has come together earlier and nicer than last year. That is already a very good step."
Although encouraged by where McLaren is, Sainz said no one at the team was getting carried away with their hopes for 2019 and thinking that success would come easy.
"The team's philosophy this year is to take it easy with predictions and with where we want to be," he said.
"Until we see what the others are doing, it's impossible to know where we are.
"We are optimistic about the directions we've taken with the concept, and the directions that we've taken restructuring the whole team - not only getting new people, but the good people that we have already at McLaren, to get them into the areas where we think they're going to exploit their talent better.
"I think we have great talent in McLaren. There's always new ideas, there's always new people coming through with great ideas and it's going to be a matter of when [we succeed].
"It's now going to be a bit of a mid-term project, I have a two-year deal to work on that, and I'm confident.
"I like what I see, I like the way the restructuring has been, and now we're ready to go racing and see where the car is, and from there start the development and the recovery."