The Norwegian missed last weekend's 4-1 victory over Liverpool with a groin strain but is now ready to return to the fold as the defending champions look to put the pressure on Premier League leaders Arsenal.
They could reduce the gap to five points ahead of the Gunners' tough trip to Anfield on Sunday.
Asked if Haaland needed to work up his fitness to be considered for the UEFA Champions League quarter-final, first leg with Bayern Munich on Tuesday night, Guardiola added: “Bayern is our last thoughts - the Premier League is every day, every week. Depends on that.”
With that said, Guardiola is expecting a tough match against the league's bottom side.
“Now every team is playing for something, it’s the same importance to fight for the Premier League as it is to stay in the Premier League,” he added.
"That’s why every game has its own characteristics and you have to be ready, because Southampton have always been so tough.
“Since the year we got 100 points [in the 2017/18 season] in the 94th minute, the game we won they were much better than us. Always it’s been a tough, tough game. Tomorrow won’t be an exception.”
Haaland is the league’s top scorer with 28 goals, six ahead of Harry Kane.
If he gets at least a brace against the Saints this weekend, he would equal the record for a player in their debut Premier League season, after Kevin Phillips netted 30 times for Sunderland in 1999/2000.
In the reverse fixture, Haaland scored the fourth and final goal of a 4-0 win at the Etihad Stadium in October.
The City striker is also just four off Mohamed Salah’s record total for a 38-match season, and six goals away from matching the all-time record of 34 goals, set across a 42-match campaign and shared by Andrew Cole and Alan Shearer.
Haaland's return to training is good news too for Fantasy Premier League managers, given he is in over 72 per cent of squads.
He was sold by more than half a million managers last week ahead of Double Gameweek 29. Presumably, many will be rushing to bring him back in for Gameweek 30.