They have been linked as possible teammates next season, with Alonso understood to be keen on McLaren bringing Sainz into the fold.
In the build-up to the Hungarian Grand Prix before the summer break, Sainz – who has since been called an attractive option by McLaren – was pressed about the prospect of partnering Alonso.
Asked if he was ready to beat Alonso, Sainz said: “I don’t know, because I haven’t even though about it, as still it’s not happening.
“I’m ready to beat anyone in the field. My racing spirit and my competitiveness and my self-confidence tells me that I can take over anyone.
“Probably Fernando would be the biggest ask that you could have on the grid, that’s for sure.
“But yeah, I would feel ready for anything.”
Sainz had jokingly responded to a preceding question about whether speculation linking him to a McLaren drive alongside Alonso was true.
“You’re going for the headline here, right,” said Sainz. “No, I cannot comment on it.”
Sainz said nothing would change until the situation became clearer at Red Bull but could be affected by Ricciardo failing to sign a new deal.
That is exactly what emerged one week after Hungary, which means Sainz has been forced out of Renault and must seek refuge either back at Red Bull or somewhere new.
The prospect of driving alongside, or replacing, Alonso at McLaren is a romantic notion given the closeness of the two Spaniards.
Sainz told Motorsport.com earlier this year that fighting Alonso on track was something he could never have imagined when he started his career, and believes it has furthered his racing education.
“I think since I arrived in F1 I have started next to him in nearly every race, which is quite strange,” he said.
“It’s something I didn’t expect, because you would expect Fernando to be fighting for world championships instead of fighting with me in the midfield at the beginning of my career.
“But what I feel particularly proud of and particularly happy is that these few years I’ve been taught by the best. I don’t feel I’ve been driving in the midfield.
“I feel like I’ve been driving for world titles, because simply to be up against Fernando in every race, also Jenson [Button], when he was in McLaren, it’s been a great feeling.
“That is what it makes me feel ready for whatever comes.”