Rory Hemmings, aged 29, dad to girls aged four and seven, died after he was stabbed in the chest after a fight inside his ex-partners home on Errington Crescent in Arbourthorne.
Steven Ray, 36, of Thornbrough Road, Heeley, is accused of his murder.
Sheffield Crown Court heard that during the altercation, the defendant picked up a four inch steak knife from the kitchen draining rack and stabbed Mr Hemmings in the chest with ‘some force’.
But Ray then tried to save Mr Hemmings who performed CPR and mouth to mouth resuscitations through instructions from a 999 operator.
Richard Woolfall, prosecuting, told the jury Mr Hemmings had split up with his ex-partner Kirsty Allen. They had two children together during their 11 year relationship.
Mr Woolfall told the jury the victim was upset about the break up and the night before his death, he had been drinking and smoking cannabis with friends.
The court heard that there had been history of verbal altercations between Ray and Mr Hemmings prior to the incident.
Mr Woolfall said: “The defendant was fatally stabbed with a steak knife. Steven Ray stabbed Mr Hemmings once in a vulnerable area on the chest.
“The blow struck the victim between two ribs just through his left lung and into his heart in which he died shortly afterwards.
“It’s the Crown’s case that the stabbing intended to kill Mr Hemmings or at the very least, inflict serious harm upon him.
“This makes him equally as guilty of the offence of murder.”
The fight, which was took place in the kitchen and living room, was witnessed by Mr Hemmings’ two young daughters.
Neighbours said they could hear the girls screaming and what appeared to be something being thumped against a wall.
The court heard Mr Hemmings had sent a text to his mother around 7.15am saying ‘I’m sorry for what I’m going to do’
His mother could tell he sounded upset and told him to ‘get some sleep’.
“This was motherly advice that Mr Hemmings did not take,” Mr Woolfall said.
“He made his way to Kirsty Allen’s home where Mr Hemmings once lived around 8am on Sunday, November 15.
“Ms Allen answered the door and the victim barged his way in. She tried to calm him down and asked him leave.
Ray was asleep upstairs who came down and also asked Mr Hemmings to leave before the pair started fighting.
The jury was told the two young girls witnessed the fight but were taken away before the fatal blow.
Mr Hemmings managed to make his way outside before collapsing.
“It was clear to the defendant that Mr Hemmings was seriously injured. He then tried to keep Mr Hemmings alive.
“When he understood he was seriously injured, he tried all he could to save his life.”
Mr Woolfall added the pathologists report found alcohol and cannabis use in his system but he wasn’t intoxicated and the effects of the drug had worn off.
Police arrested the murder accused and Ms Allen after Mr Hemmings’ death.
The court heard it soon became clear that Ms Allen was not involved and was released without charge.
In a police interview Ray told police Mr Hemmings was gesturing to his pocket and thought he would use something to hurt him with.
He told police he was scared for the safety of Ms Allen and her two children.
Police did find a small knife on Mr Hemmings but the prosecution claim it never left his pocket during the fight.
Ray, who was wearing a blue long sleeved Lyle & Scott polo top in the dock, denies murder.
The trial continues.