Jenson Button reiterated his belief that testing McLaren's new-spec MCL32 in Bahrain earlier this year would have been "useless".
The Brit was called upon by McLaren to sub this weekend at Monaco for Fernando Alonso, and as a consequence he ramped up his physical preparation and spent considerable time in the team's simulator, but declined to drive in F1's in-season test in Bahrain.
"Preparation has been good, apart from the fact I haven't driven the car, these new regulations," Button said on Wednesday.
"It's not perfect but the option was to do half a day in Bahrain, which I thought was useless for me to do, a completely different circuit.
"So I said to the team I thought it best if I did the simulator. I have spent a lot of time in the simulator getting used to it.
"It will be interesting, there are a few things different, with the regulations and year-to-year with the technology, but it is still a racing car.
"In hindsight it's always easy to say that I would have done 17 laps the day I would have tested - and only half a day!
"Bahrain is a different circuit to here. I think as long as you understand where the car is working, and running through today – those are the things you need to understand and those are the things you can do in the simulator.
"It is wider, which is the big thing for me. The way the tyres work, you work your way around it, and it is warm, which helps."
Despite the challenge of jumping straight into the fire this weekend, the 2009 world champion said he felt no particular pressure on the eve of his return.
"I am very relaxed, very excited actually. It is interesting coming back for one grand prix.
"Monaco it is very special. I've won it before, done it for 17 years and had some really good experiences. But I don't feel any pressure at all.
"I will get in the car and do the best job I can and everything I do, I will get the best out of myself and get the best out of the equipment and team I am working with.
"The car was working well in Barcelona qualifying. I drove the upgrade in the simulator and it was a definite improvement. If it is all straightforward this weekend, we should be reasonable."
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