Gianluigi Buffon has hinted he will not definitely retire at the end of the season as expected and said Leonardo Bonucci may be regretting leaving Juventus to join AC Milan last summer.

Bonucci's €42 million transfer to AC Milan was one of the biggest shocks of the last transfer window, with the 30-year-old leaving the Bianconeri after winning six successive Serie A titles and appearing in two Champions League finals.

He was immediately appointed Milan's new captain, but has endured a difficult first half of the season which has concluded with the Rossoneri down in 11th position, 14 points behind the top four and five adrift of qualification for the Europa League.

Buffon is still in regular contact with his former teammate, and he feels he is starting to regret the move he made.

"Leo is like a brother to me because I like even his excesses," Buffon told La Gazzetta dello Sport. "He's got healthy values and, when placed in a certain context, he's a point of strength; an incredible resource.

"The environment at Juve was perfect for him and I was sorry to see him leave because it seemed like it was an impulsive decision, driven by pride. I've told him this when we chat from time to time and he told me that it was not impulsive but rather a pondered decision.

"Leo lives for challenges and he needed to reignite that fire with a firm, unpopular decision. I respect it, but I was sorry and I think that he's also very sorry about it now."

Gianluigi Buffon announced his retirement from international football with Italy following their failure to qualify for the 2018 World Cup. Getty Images

Buffon also has a decision to make over his own future as he appears to regret announcing his plans to retire following Italy's World Cup playoff defeat to Sweden.

The 39-year-old, who turns 40 this month, appears to be having second thoughts over whether or not to play on again next season, even though he feels under no pressure to decide either way.

"No footballer wants to retire, but no, I'm happy because I've reached an important stage in my life and I'm serene," he said. "Arriving at such a crucial junction with this inner harmony is all that matters and it's truly amazing.

"I know how things work out there on the field and I could say I'll still be the way I am now when I'm 60, but there are so many considerations to make, not least considering how lucky I am to be in a club where I am appreciated and where I have an extremely strong bond with everybody, from the president all the way down.

"I feel I am totally part of the project. The president's extraordinary with me. For the past five years, he's been telling me 'at a certain stage of the season, come to me and tell me if you want to continue or not,' and that's what I'll do this time too.

"At a certain stage, you need to understand in what role you can be most important for the cause. Many people have told me I had exaggerated by saying what I did with the national team, but a 40-year-old has got to have a sense of responsibility.

"Since I wasn't born yesterday and I know that I could be a burden, I would rather step aside. I will never be a problem, but for those who have given me so much -- Juve and the national team -- I will always be available, in any form and in any role."

Buffon confirmed that he will definitely play on until December should Juve win the Champions League, "so I can play in the Club World Cup", while he says that his likely successor for Italy, Gianluigi Donnarumma, would not make a mistake by joining Juve and taking his number one jersey there too.

"Well, you never go wrong with Juve," Buffon said with a smile when asked if he would advise Donnarumma to stay at Milan or come to Juve. "I can't give any advice to Gigio because I am not living in his situation and I don't know what emotional connection he could have with Milan. I could tell him a few things, as I have done with the national team, but what makes the difference is what resonates within you."