A Sydney man whose assault of a baby left the nine-month-old boy disabled has received a minimum sentence of eight-and-a-half years in jail.

Eduardo Varas, 33, had pleaded guilty to two counts of grievous bodily harm over the attack at a Lalor Park home two years ago.

Today, he was sentenced to 13 years in jail with a non-parole period of eight years and six months.

The baby's mother had left her son in Varas' care for an hour, and returned to find his "lifeless body surrounded by paramedics".

Eduardo Varas has been sentenced to 13 years with a non-parole period of 8 years and six months. (Supplied)

Trauma doctors told investigators that Varas had inflicted at least three acts of violence on the baby.

Judge Rodney Madgwick said the "injuries to the child can fairly be called catastrophic".

Today, the baby's mother said "no sentence would ever have been enough".

"I really thought it would be on the higher end – eight-and-a-half years for what he's done? Not good enough," she said.

The baby's mother said she felt "absolutely disgusted and betrayed by the system".

"We've been given a life sentence... it's really not good enough," she said.

Earlier this week, she told the court she felt "guilty" for not protecting her son.

READ MORE : Mother describes horrific injuries carer inflicted on baby boy

The baby spent three weeks on life support after the attack, and had part of the left side of his skull removed and a permanent shunt inserted into his brain.

He will need care for the rest of his life.

"He's beautiful, he's an amazing and strong beautiful boy and I'm so glad he fought so hard to stay here and be with us all," his mother said.