Fernando Alonso is expecting as little as "two-tenths" to separate up to nine cars in qualifying for this weekend's Spanish Grand Prix.
After an anonymous start to his comeback season, Alonso went on a late charge to finish eighth last time out at the Portuguese Grand Prix.
On home soil the Spaniard has once again shown his pace, setting the fifth-fastest time on Friday afternoon for Alpine and only slower than team-mate Esteban Ocon by half-a-tenth.
With less than one second separating Lance Stroll in 14th and pace-setter Lewis Hamilton, Alonso believes the margins will be reduced further during qualifying.
"It is only Friday, it is only practice and you never know what everybody is doing on Friday," he said. "Even from us, I think there is more to come when we put it all together.
"But we are trying to spread the programmes into Friday with both cars trying different things at different times of the day in practice and I think the overall feeling is good but we don't know.
"I think qualifying is going to be very tight. It's a short lap so I'm thinking two-tenths is going to be eight or nine cars and we want to be at the front of that pack."
After the Australian Grand Prix was pushed back from its position as the season opener to November, pre-season testing was moved from Barcelona to Bahrain in a bid to reduce costs with the Gulf state also hosting the first race of the year.
Having completed the first day of running two months later than planned, Alonso added: "It was the first time here this year with these cars and it felt good, it felt fast all through free practice.
"[The car was] well balanced. It is still only Friday and there are a lot of things to analyse.
"We brought little updates here and we are still analysing them but I'm happy with a trouble-free day."
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