Smith, who agreed a new two-year contract this week, has recovered from a groin injury and will definitely be in the team, according to his coach, Andy Goodway.
"He's 100 per cent certain to play, but he could be in either position," said Goodway. "His experience is invaluable for us. He's had a little rest, he'll be fresh as a daisy and we'll be looking for him to do a bit extra.
"Tony has signed a new contract because he likes being at Wigan and playing in the big games - and there are none bigger than this."
Wigan inaugurate their new home at the JJB Stadium against a side that has beaten them twice this season.
"It's not often we go into a game against Castleford as underdogs," said Goodway. "As for losing home advantage, we've been training at the new stadium and I think the players have settled in."
Apart from Smith, Goodway has also added Neil Cowie, who missed the match at Wakefield through family commitments, to last week's 17-man squad, while the Castleford coach, Stuart Raper, will have Nathan Sykes fit after missing last week with a leg injury.
Raper knows from his experience in his native Australia just how difficult it is for a fifth-placed team to win the play-offs. "Having to play every team above us away from home is hard, but it has been done. We have to take it one step at a time and we have a big job to start with on Sunday," he said.
In tomorrow's other game, Widnes have to set aside their grievances at losing the argument over home advantage and repeat their victory at Hunslet of two weeks ago if they are to reach the Northern Ford Premiership's Grand Final against the already qualified Dewsbury.
Gateshead Thunder, who came so close to making the Super League play- offs in their inaugural season, have become the first club to name their squad for next year.
There are no places for the Allwood twins, Sean and Richard, their fellow Australian, Brett Grogan, or the unlucky Stuart Singleton, who missed the whole of the season with a knee injury.
Martin Offiah is among the players released by the London Broncos, while another former Great Britain three-quarter, Paul Loughlin, has been told he is not being retained by relegated Huddersfield.
The New Zealand prop, Quentin Pongia, who captained the Kiwis to victory in England last autumn, will miss the Tri-Series against Great Britain and Australia next month in order to have an operation.Reuse content