Jenson Button believes former McLaren teammate Fernando Alonso has "finally made the right decision" after announcing he would quit racing in Formula 1 at the end of the 2018 season.

2009 F1 world champion Button spent two seasons as Alonso's teammate at McLaren before leaving F1 at the end of the 2016 season in order to take a break from racing.

Shock Moments of F1 2018… So far Video of Shock Moments of F1 2018… So far CrashTV: Video Thumbnail:

Despite a one-off return in Alonso's place in Monaco last year, Button has ruled out a full-time return to F1, instead focusing on his duties in Super GT and the FIA World Endurance Championship.

Alonso confirmed on Tuesday he would not be racing in F1 in 2019 in order to take on "bigger challenges", and is thought to angling for a move into IndyCar next year as part of his push to complete the 'triple crown of motorsport'.

"I said to him he’s finally made the right decision. He’s woken up and smelled the coffee, as we say," Button told reporters at Silverstone on Saturday following WEC qualifying.

"He’s finally made the right decision. It’s always down to the individual when they choose to leave Formula 1. He’s done the same thing as what I chose to do, leave but leave it open for one year after to go back.

"I think that’s the right option to do. But if the McLaren’s quick and it’s winning races, he’ll be back in Formula 1."

Button was full of praise when reflecting on Alonso's time in F1, but said he still expected the Spaniard to have a busy racing schedule in 2019 and show no signs of easing off.

"Discussing his retirement means nothing, it’s more his career, it’s been exceptional. To win two world championships and be close on a couple of other times, there aren’t many people who get to do that," Button said.

"We were teammates, so I know exactly the strengths and weaknesses for Fernando. It was really, really enjoyable racing with Fernando and against him as a teammate. My toughest teammate, really enjoyed it though. My late father always respected Fernando, and that’s always a good judge of character. He used to get on very well with my father as well, Fernando.

"It's really nice to race with him. Tomorrow we start second and third on the grid, which is quite cool. But he’s still going to be racing until he’s 95 years old. He races more than me, he’s at the karting school in Spain all the time, driving, teaching. He’s obviously racing in WEC.

"I think next year he’ll still have a busy schedule. You can’t stop a racing driver racing. I thought I could stop, but I can’t."

Alonso said on Thursday that F1's poor on-track action was the main reason behind his decision to quit, but Button doubted he would find close competition in the WEC given Toyota's current dominance in LMP1.

"I love the way he said though that the racing isn’t as much fun," Button said.

"It’s like, 'hang on a sec, you’re racing in WEC and you’ve got one car to compete against!' You shouldn’t really be making the call on that.

"I know that he loves IndyCar, and I think he was really comparing it to IndyCar, and his experience at the Indy 500.

"If he’s racing for a win, he’s going to enjoy it a lot more, and you do. But when you’ve won multiple world championships like him and you’re fighting in the midfield, it does get boring after a while.

"You want to be at the front, not getting lapped by the leaders."