Fernando Alonso showed positive signs during Indy 500 practice on Monday, but anticipates a far greater challenge come the race.
The Spanish two-time Formula One world champion was 19th fastest of 32 drivers who took part in the opening-day practice.
In his McLaren Honda Andretti entry, Alonso was quickest in the session for rookies and veteran refreshers as he continues preparations for the May 28 race.
"The most difficult thing will be the race itself - all the things that happen in a race like this one, which are the traffic, running in traffic and learning all the little tricks to overtake," he told a news conference afterwards.
"Then to use the performance of your car in which moment of the race [and] why.
"All these little things that only with experience and with races you can learn. I don't have that experience and I don't have that time, so I know that I will be weaker in some of these aspects.
"I need to learn as quick as I can in the next 10-12 days."
Marco Andretti was the day's quickest driver, going 0.5907 seconds faster than Alonso.
Alonso is skipping the 2017 Monaco Grand Prix to compete at the Indy 500 on the same day.