Mauricio Pochettino will walk headfirst into a supporters' protest when he takes charge of Southampton for the first time against Everton on Monday after the club acted ruthlessly by sacking Nigel Adkins to safeguard their "long-term ambitions".

The Argentinian, capped 20 times by his country, must also win over a playing squad left surprised and confused by Adkins's dismissal, given the team have lost only two of their past 12 Premier League games and drew at the European champions, Chelsea, only on Wednesday to move three points clear of the relegation zone. Fans have strongly criticised the decision and intend to wave white handkerchiefs after five minutes of Monday's televised game against Everton.

The club's executive chairman, Nicola Cortese, was absent as Pochettino was unveiled on Friday after signing a two‑and-a-half-year contract, with the new manager revealing he had been "researching Southampton for several weeks". "[Gaining] the kindness of the supporters is the biggest challenge I have," said Pochettino, who will take charge of his first training session on Saturday, through an interpreter. "They are the biggest part of this club and I hope I can convince them with honest and hard work. I have spoken to people like José Mourinho, who is a good friend of mine, about the Premier League. He told me the best football in the world is being played here."

Pochettino, whose new squad has been bolstered by the £3.5m arrival of the Norway centre-half Vegard Forren from Molde, added he had the "greatest sympathy and respect" for Adkins, who had hoisted the team 51 places in 26 months in charge and boasts the best win percentage – 54% – of any Southampton manager since the 19th century. He had been informed that he was to be relieved of his duties in a meeting early on Friday morning, despite having a contract through to 2016.

Cortese had previously considered the manager's position after the defeat at West Bromwich Albion in November but, having resisted a change then, the sense was that the situation would not be reviewed again until the end of the season. Yet he is understood to have retained doubts over whether the man who had steered the club to successive promotions had the authority to thrive in the Premier League, and it now appears the availability of alternative candidates was key to Adkins having survived up to now.

Pochettino's dismissal by Espanyol, who were bottom of the Primera Liga at the time, at the end of November allowed the hierarchy to pursue their preferred candidate. "This decision has been made with the long-term ambitions of Southampton in mind," said Cortese in a statement. "Whilst we acknowledge the contribution Nigel has made during the past two years, for the club to progress and achieve our long-term targets a change was needed."

Adkins' dismissal was greeted with disbelief by Southampton's supporters. "The fans were 100% behind Nigel," said Mike O'Callaghan, chairman of the Southampton Independent Supporters' Association. "He's got us two automatic promotions, we're 15th in the Premier League, so what has he done wrong? It's farcical what's going on.

"It's not as if we've poached a manager from an established club and can say we're moving to the next level. He's unknown and unproven, and was sacked at a club bottom of the Spanish league. All we've known is success under Nigel Adkins at Southampton. Previous chairmen have made us into a joke, and now the present [executive] chairman is doing the same."