Russell Martin, his feet fiddling with a ball, is discussing Southampton’s record-breaking run in his office overlooking the main pitch at the club’s sleek Staplewood training campus on the edge of the New Forest, a 24-game unbeaten streak underpinning their striking evolution into formidable opposition. They have not lost in 21 Championship matches and boast higher average possession than any club in Europe’s big five leagues, where Manchester City, Paris Saint-Germain and Barcelona lead the way.

Southampton, who have won 10 home games on the bounce in all competitions, conceding only three goals, are marching under Martin. At the start of the season, when 31 players reported for training, the door to this room was rarely left alone. “Probably three-quarters of those [players] had come in at some point and told me they either wanted to leave or were expecting to leave,” says Martin, a key cog in the club rebuild last summer that included the appointments of a new director of football, Jason Wilcox, and chief executive, Phil Parsons.

Many players did depart but Martin supplemented a talented core and convinced others to push for an immediate return to the Premier League. “The energy at the start was just a bit broken, a bit hurt. There was so much change – three managers last season – and so many people left the building, staff as well as players because it affects jobs when you get relegated. There was a bit of self-preservation because you don’t want to open yourself up to another group of staff straight away. It takes time to build some trust and relationships.”

Southampton’s second goal in the victory against Watford on Tuesday, which earned an FA Cup fifth-round trip to Liverpool, epitomised the sharp edges of Martin’s mantra. In 17 seconds, they flipped from back to front, a six-pass move that began with the goalkeeper Joe Lumley playing out under pressure on his goalline culminating with Sékou Mara lashing it into the net. Tyler Dibling, a 17-year-old who joined the academy aged eight, carried the ball from midway inside his own half, driving forward about 40 yards. “You can’t have courage if you’re being asked to do something you don’t believe in,” Martin says. “It’s impossible.”

He is talking the day before Southampton sealed that trip to Anfield, before which his second-placed side have five league games to improve their chances of automatic promotion, starting at home to Huddersfield on Saturday. Four straight defeats in September, lost by an aggregate of 12-2, feel a lifetime ago. “I think that period was important because we didn’t change the way we behaved,” the 38-year-old says. “There was no tension or anxiety in here. We don’t criticise them for making mistakes, if the intention is right and clear. The only time they get criticised is when they’re not brave enough, when they don’t run hard enough. ‘Did you have the courage to take people on in the final third, to build up in our six-yard box when someone is pressing you like a lunatic? Did you have the aggression with and without the ball?’”

At midday the players file into the auditorium for an analysis meeting: a quick debrief of their 2-0 win over Rotherham before Martin announces his team to face Watford, including another youngster, Jayden Meghoma, the 17-year-old left-back signed from Tottenham last year. Martin runs through a few clips, assembled by the tactics and insights analyst, Ben Parker, starting with a kick-off routine that almost resulted in Ché Adams scoring. He shares his delight at his players’ work off the ball and praises their desire to attack in numbers. “We play forward, we run forward,” Martin says, matter-of-factly. Rotherham had two shots on target, one in the 94th minute, which he flags. “It shouldn’t happen … I was fuming. It’s my job to always want more.”

Southampton’s appetite to regain the ball has been pivotal to their form and their average 65.9% possession. “There is a purpose to every action. Sometimes the action is going to be 80 yards away from the opposition goal, and other times 10 yards. I don’t feel like we ever pass the ball for the sake of passing the ball, so I am proud of it because it takes a lot of work. That’s the whole plan for us, to have the ball as much as possible and to dominate territory as well, to play in the opposition half as much as we can.”

Twenty minutes later the players head on to the pitch, Martin and his assistant, Matt Gill, joining the rondos at the start. On Fridays the pair line up when the coaching staff take on the media team at eight-a-side. Colin Calderwood, appointed first-team coach in October, has also starred. “He keeps me calm … I’ve got less bookings since he’s come in.” The squad practise set pieces before a small-sided game and penalties after. At the end of the session, Martin leads the youngsters Nico Lawrence and Cameron Bragg through a passing exercise with the help of the first-team sports scientist, Rhys Owen, among those to follow Martin from Swansea. “Every detail counts,” Martin says, encouraging Lawrence to open his shoulders to improve his positioning.

Last week Sport Republic, the ownership group that acquired the club two years ago, was in town, the lead investor, Dragan Solak, and Henrik Kraft congratulating the team on their unbeaten run. “At the start of the season,” Martin says, “there were so many times I stopped [clips] and said: ‘This is not going to be us. The distances in the team are too big, too many of you jogging back to goal and if it carries on, you just won’t play.’ That is the biggest difference to where we are now: the amount they want to run for each other, fight for each other, recovery runs. I feel like when you have the ball you have to show a certain amount of confidence and almost like swagger … what we’re asking them to do with the ball, you can’t do that without that mentality. But you have to balance that with the humility to run.”

After victories, Martin fist-pumps towards supporters a la Jürgen Klopp, with whom he will soon share a touchline. “I look at him and I love the authenticity he and Guardiola show; they are completely themselves. We are going to go to Anfield and try and be the team we want to be. If we get beat, it will be my fault because of the way we play, I know that and I’m already aware of that. ‘You can’t go to Anfield and try and play that way’ … but why not? That is the challenge for us and the challenge for me is to always be the leader I want to be, the person I want to be. For those guys to do it at the highest level is incredible.”

Staff at the club speak of a refreshing, inclusive culture. Before Christmas, backroom staff enjoyed a trip to Bournemouth in fancy-dress Ali G costumes. Naturally, it helps when you are winning but Martin’s hands-on approach has helped re-energise a club that had grown stagnant. He set out his stall on punctuality on day one. “If one person is late, the whole team will run at the end of training,” he says. “It is the same on a Saturday. ‘If one of you doesn’t want to press, you’re all going to run more. You are responsible for each other.’ On the first day someone was late, they ran. On the second day, someone was late, they ran twice. There isn’t a problem with that any more.”

Southampton, a point clear of Leeds and two of Ipswich, may be top of the leaderboard for unbeaten runs and possession but it is the top division they crave to be in. “I’m immensely proud of the players and grateful to them for what they have done – they have made history, which is brilliant for the club,” Martin says. “But my overriding feeling is it will be forgotten about and not mean as much if we don’t achieve what we want to achieve. Our job now is to make sure we don’t overcoach them, we don’t complicate it. I think we are in a brilliant place and we need to keep them there as long as possible.”