Southampton owner Katharina Liebherr has pledged not to sell any players during the transfer window.
The club's interim non-executive chairman has backed manager Mauricio Pochettino's stance that Saints will not let any top stars leave St Mary's this month.
Executive chairman Nicola Cortese resigned on Wednesday night amid a long-standing impasse with owner Liebherr over the club's future direction.
Cortese's exit plunged a host of the club's plans into uncertainty, but now Liebherr has moved to quell the question marks.
"The club has no plans to sell any of the squad during the January transfer window," said Liebherr in a statement to Southampton's official website.
"The manager and the team have my full support."
The resignation of his mentor and boss Nicola Cortese on Wednesday night could well see Pochettino leave Southampton in the summer.
The former Espanyol boss has pledged himself to Saints until the end of the season, but offered no further assurances.
Liebherr has vowed to recruit a chief executive to replace the 45-year-old Cortese. Former Liverpool managing director Christian Purslow is understood to be in the running to fill the new position.
Rumours persist that the construction machinery magnate will look to sell the club, that her late father Markus guided out of administration in 2009.
Pochettino is unsure who currently handles Saints' transfer business, but said he will focus his attention elsewhere.
"We've got to concentrate on the group of players we can bring back to fitness and assimilate back into the squad and the team," he said.
"Artur Boruc and Guly do Prado are still coming back from injuries and we need to make sure Victor Wanyama can do the same quickly."
Full-back Calum Chambers should be available for the Sunderland trip after illness, with striker Dani Osvaldo still missing as he completes his three-match ban for violent conduct in the 1-1 draw at Newcastle in December.
Pochettino has been at pains to reassure his squad about the future, at least short-term, and is battling for calm ahead of the Wearside clash.
Press Association Sport understands there is still widespread unrest among the Southampton squad, with players keen for further answers from the ownership.
Pochettino will press for more information from Liebherr in the next fortnight, but said there is no opportunity before Saturday's lunchtime Sunderland fixture.
"It is only natural that everyone would be reacting to all this," he said.
"It is hard to predict what the effect on the players will be.
"It's clear that it may affect the players as they all have varying degrees of relationship with Nicola Cortese, and of course his leaving may affect us in some way.
"In those situations it's clear that maybe some minds will be focused on what happened on Wednesday, rather than on Sunderland on Saturday. But we have to be professional.
"We have to be fully focused on the game on Saturday and, as always, try to get a positive result."