Thavisha Lakindu Peiris, 25, "bled to death" in his car in Southey Crescent in Sheffield on 27 October.
Shamraze Khan, 26, of Southey Crescent, pleaded not guilty to Mr Peiris' murder at Sheffield Crown Court on Monday.
Kasim Ahmed, 18, of Main Road, Darnall, pleaded guilty to murder and will be sentenced later this month.
Mr Peiris was working as a Domino's Pizza delivery driver after graduating in IT from Sheffield Hallam University and was due to start his "dream job" shortly after he was stabbed in the chest and killed.
The court heard the defendants carried out a knife robbery at Castle Market in Sheffield earlier that day, where they had stolen two mobile phones.
The men attacked Mr Peiris that evening to steal his phone, the court was told.
"They took the keys of his car and and left him to bleed to death in the driver's seat," the prosecution said.
After his arrest, Mr Khan told police he saw Mr Ahmed pull out a knife and stab Mr Peiris in a "frenzied attack", but claimed he did not know he was carrying a weapon.
He said he was unable to stop him, but did not encourage or take part in the attack.
But the prosecution claimed both men were carrying knives that night and were jointly responsible for the attack and guilty of murder.
Mr Peiris, originally from Sri Lanka, was described as "friendly and gentle" by his family.
The trial continues.
A pizza delivery driver was killed in a "frenzied" knife attack by two men trying to steal his phone, a court heard.