It is a wonder that Billy Sharp can get the words out. Each little detail intensifies the emotion. The images that flash before him range from the angelic to the disturbing, yet they come together in unbearable sadness. The Southampton striker lived every parent's worst nightmare in October when the life of his baby boy Luey lasted no longer than two days. Sharp felt him take his final breath.

Less than 72 hours after Sharp and his first child had spent their last moments together, in front of Match of the Day at the children's hospice, he was playing for Doncaster Rovers, his club at the time, against Middlesbrough in the Championship. And with the sweetest swish of his left boot after 14 minutes, he scored. "That's for you son," read the message on Sharp's vest, in the frenzied goal celebrations. The next day was Luey's funeral.

In the week that has seen football unite behind the heart attack victim Fabrice Muamba, and in the season when Gary Speed's death brought similarly strong communal outpourings, Sharp's inspirational story stands as a symbol of the game's capacity to overcome.

"I played against Middlesbrough because the longer I'd have left it, the harder it would have been," Sharp says. "I wanted to play on the Saturday against Coventry City when Luey was still here and the only reason I didn't was because if I'd have come back and he'd have died, I'd never have been able to live with myself.

"I was feeling sorry for myself, I wanted to change that and the one thing that could do that was football. It is a very special sport. We've seen over this past week what it can do, although it shouldn't take what happened to Luey or Fabrice and other players to remind people why football is so special."

Luey was born on Thursday 27 October with gastroschisis, the birth defect that causes a rupture of the abdominal wall, which exposes the intestines. It had first shown up on the 12-week scan of Jade Fair, Sharp's girlfriend and, by 14 weeks, it had been confirmed. Yet there was no need to panic, merely for the hospital to monitor the situation.

The couple were cheered by the 95% survival rate of babies with the condition. Luey was not in distress, according to the scans. It is difficult to gauge the severity of gastroschisis during pregnancy and the view was that they would have to wait and react upon delivery.

The speed with which Sharp and Fair were plunged into the whirlwind journey with Luey was one of the many hideous things. "He was six weeks early," Fair recalls, "and when he came out, the medics' faces just dropped. They knew straight away that they wouldn't be able to save him, although they didn't tell us at the time."

Luey was wrapped in clingfilm and wheeled to surgery. It tends to last up to three hours but he was back after one. In intensive care, the truth was etched upon the doctors' faces. And so Luey began his fight. He stopped breathing 10 times that day and he turned blue, but on each occasion, he would summon something and recover. "He'd make this funny noise," Sharp says. "I hear it sometimes. It will never go away."

Luey got through the night, under the gaze of his parents; he was not supposed to last this long and, in the morning, they arranged to take him to the Martin House hospice. They were told that he would probably not make the ambulance. He did; and in the soothing surrounds of what felt like a family home, he got through another day and another night.

Saturday brought the inevitable. The deterioration in the evening was quick. "The staff upped his pain relief," Fair says, "and made him more sedated, which was hard because then his eyes were completely shut. He didn't open them again."

"When he'd stop breathing," Sharp says, "he'd somehow muster this big, deep breath and he'd sort of shake. When he did it for the last time, it was as if to say: 'This is it now,' and he went. And his body just relaxed. He cried on that last breath. That was the only time, apart from when he was born, that he'd cried. That was when we were watching Match of the Day."

Sharp's strength of character is staggering – so is Fair's – and he has needed it to rise above some scarcely believable abuse. On 2 January, in the derby at Doncaster's Keepmoat Stadium, a Barnsley fan chanted a song that mocked Luey's death and last month, after Sharp had completed his £1.8m transfer to Southampton, a Twitter troll spouted similar bile.

Sharp prefers to remember the overwhelming support that he has received from within the game. On his second appearance after the tragedy, he scored again, at Ipswich Town, and the home crowd applauded as one. They also chanted Luey's name. Sheffield United, the team Sharp that supported and played for, offered a tribute at Stevenage; the travelling fans began a minute's applause in the 24th minute, Sharp having worn the No24 shirt for them. Blades players wore black armbands, as did those of Derby County against Cardiff City. The messages and letters of condolence flooded in from as far afield as Australia, the United States and China. Sharp was touched that his idol, Michael Owen, made contact.

"Against Barnsley, it was one fan," Sharp says. "And I think some of the Barnsley fans heard it and they dealt with it, which was good to hear. I'd like to make it clear that I don't think it was all of the Barnsley fans that were chanting it. But that one fan and the other person on Twitter … I don't even know their names so they don't mean anything to me. It hasn't affected me."

The end of 2011 was impossibly bleak for Sharp, with Speed's death adding to the pain. "I played with Gary at Sheffield United," Sharp says. "He was a team-mate, a friend … one of the most honest, hard-working and loyal people you'll meet. I was getting changed for a christening when I heard. I was a godparent to one of my friend's little boys, which was obviously going to be hard. I was in shock when I heard."

For Sharp, the challenges keep coming. He is determined to establish himself at Southampton – the visit of Doncaster on Saturday will be poignant – and he believes that the club is Premier League-bound. Off the field, he and Fair are endeavouring to help families affected by gastroschisis through the Luey Jacob Sharp Foundation.

Luey will always be their shining light. "I know that Jade counts the days since he went away," Sharp says. "Even when you have a minute where you're not thinking about him, you'll walk past a picture and it makes you smile or you'll think: 'Why isn't he here?'

"It's going to be hard when we come to the first year anniversary of his birth and then, a couple of days later, it will be the anniversary of when he passed away.

"I do wake up some days and think: 'Why can't he be here?' and: 'I don't want to go to training,' but I realise how lucky I am to be a professional footballer. I do believe that if he were here, crawling along the floor, he'd want me to do my best whenever I went out on the pitch. Everything I do, I do for him."

Follow the Luey Jacob Sharp Foundation on Twitter @Foundationljs