Smith's 115 was his second century of the series and helped Australia to finish the opening day of the Fifth Ashes Test with 326 runs on the board and England already under the cosh at 8-1 as they battle to avoid a 5-0 series sweep.
It was a fifth rescue act in five Test matches in the series from Haddin, who came out 10 minutes after lunch with Australia reeling at 97-5 and scored a 90-ball 75 in a sixth wicket partnership of 128 with Smith.
"It's been outstanding hasn't it?" grinned Smith. "Being in tough circumstances, he just comes in and tries to shift the momentum of the game. He's done it on numerous occasions in this series and credit to him, he's played beautifully. To be able to bat with him and form another partnership was great for the team."
Haddin, 36, had to wait until Adam Gilchrist retired in 2008 to make his Test debut at the age of 30 and it has hardly been plain sailing since.
After playing in two lost Ashes series, he walked away to be with his daughter Mia as she battled cancer two years ago. Haddin showed great resilience to win back his place in the side this year before embarking on his fourth Ashes series still looking for his first triumph.
But it is not just the 465 runs at an average of 66.42, nor the five half-centuries and one century he has scored in his last seven innings against England that have made him such a thorn in the tourists' side.
It is more the timing of his interventions, repeatedly standing up when England have done what is perceived to have been the hard work of removing Australia's top order.
Having been through three successive Ashes series defeats, there is no doubt at all that he is thoroughly enjoying Australia being on top against their oldest rivals. "I think Brad enjoys getting into a little bit of banter on the field and he certainly thrives when the England players are coming at him and he's done it beautifully all series," Smith added.
Haddin is paceman Mitchell Johnson's only rival for player of the series honours and Smith laughed when asked about rumours circulating on Twitter that the Sydney Test might be his last before retirement. "It's news to me," Smith said.
"Brad's in the form of his career at the moment. It's up to him if he wants to leave the game, he's certainly playing great cricket and he'd be a big loss to the Australian team, that's for sure, if he does decide to retire."