The duo were part of the Italy side that fell to a 1-0 aggregate defeat to Sweden, meaning that Italy will be absent from the tournament for the first time since 1958.
Both players retired from international duty after the game, with Allegri revealing that the pair would be excused from their return to club action due to their exertions.
'They're getting over the disappointment but after 15 days with the national team they spent a notable amount of physical and - above all - mental energy,' he explained ahead of the game.
'It would have been Buffon's sixth World Cup and it was a big disappointment. But I found him in form. He had a good reaction.'
Buffon ended his Italy career with a record 175 caps to his name.