The Scot had feared that Saturday's match against Liverpool, which ended in a 3-1 defeat, would be his last as Bluebirds manager after disagreements escalated between him and owner Vincent Tan.
However, a temporary truce appears to have been called while the two work out their differences and Mackay will hope for some festive cheer against a Saints outfit who have not won in six Premier League matches.
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While the sides have met regularly in the Championship over recent years, this will be their first fixture in the top flight and Pochettino is eager for his team to show their resilience.
"We have to keep on working and believing as a team," he told the club's official website. "In the past we had a run of seven games winning when we were looking up but now it is the opposite. We need to keep working."
Mackay will take comfort from his side's home form going into the game, with Cardiff having earned 11 of their 17 points at home.
Luke Shaw (illness) and Nathaniel Clyne (hamstring) look set to return for Southampton but Victor Wanyama (calf), Artur Boruc (hand) and Guly Do Prado (knee) will miss out.
Cardiff however have just one injury doubt, with Craig Bellamy unlikely to feature due to a knee injury.
"Craig has a little knee issue right now," Mackay told Wales Online. "It's an ongoing situation. He has had a number of operations on the knee over his career and he is being checked out."