Former F1 world champion has dismissed concerns of a Red Bull 'walk in the park' this season.
Max Verstappen cantered to victory in the Bahrain Grand Prix season opener, finishing 12 seconds ahead of team-mate Sergio Perez with a further 26 seconds over Aston Martin's Fernando Alonso.
The dominance shown by the RB19 in Bahrain led to many of its rivals suggesting the championship was already in Red Bull and Verstappen's hands.
But suggesting the title is far from a foregone conclusion, Button said: "I watched the race and the Red Bulls are out in front – it looked like a relatively easy race, especially for Max.
"But I have to say, forgetting who won the race, it was a great race.
"It was too easy for Max, yes it was, but the race itself was great – I loved the action.
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"To see two multiple world champions going at it, Lewis and Fernando, it was pretty special.
"I know a lot of drivers have said it is going to be an easy championship for Red Bull and Max, but how can you say that?
"We have only tested one track, we have only raced at one track. We all know Bahrain is very unique in the way that the cars work there.
"It is a heavy-breaking, traction circuit. It is not so much about high speed so we can't say that."
Button seeking Saudi answers
"I think we will understand a bit more after Saudi which is a bit more of a high-speed, flowing track, and also when we get to some of the European races," added the 2009 world champion.
"So no, it is not a walk in the park for Red Bull and Max. It is a great start to the season and better than the one they had last year but I think we are going to have some very close fights.
"I don't think it is going to be a straightforward win for Red Bull and Max."
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