Sainz’s best effort ensured Ferrari remained at the head of the timesheets, with the Italian marque impressively securing a 1-2 classification in both Friday sessions.
When asked to assess Aston Martin’s chances this weekend, Alonso said: “Let’s see tomorrow, I think today is just getting confident with the car and the track.
“I think Ferrari is probably out of reach, again like Monza they are a little bit too fast, Red Bull will be fast tomorrow when it counts, so it’s very tight, you can be P5, 6 or you could be out of Q3, you can be P12 because within two tenths there a lot of cars.
“So it’s gonna be tight, we have to be ready for anything and nail the lap in Q2 and Q3.”
This weekend’s race weekend in Singapore has witnessed the drivers presented with the challenge of a revised track layout.
Construction work taking place at the Marina Bay has prompted the removal of the sequence that previously made up Turns 16-19 and the addition of another straight.
Alonso, who has raced in every Singapore Grand Prix bar one and is a two-time winner at the venue, asserts the changes have improved the circuit for the better.
“Yeah it was fun, I think it was an improvement from the past, it’s a little bit faster and you get the rhythm into the lap, so, yeah, I like the change,” he added.
“It was a normal Friday in Singapore, hot and get some tests done on the car, so let’s see tomorrow.”