The 24-year-old victim had just finished work at a nearby eatery on the promenade, just before midnight, when he saw a young woman allegedly being assaulted by a man.

As he stepped in to help, the offender allegedly produced a knife and stabbed him in the left side.

The victim was left with non-life threatening abdominal injuries and sought help from a nearby late-night parking attendant, police said.

The man was arrested on Grimshaw Street in Greensborough about 2.45pm Monday.

He reportedly drove a blue Commodore into the intersection of William and Grimshaw streets, where it collided with Mercedes van being driven by a member of the public. Police then swooped and arrested him.

"He was on the ground, with police surrounding him, thrashing about a little bit," witness to the arrest, Tegan Mutmer​, told Nine News.

"There would have been close to 15 police cars, if not more."

Two other men were also arrested, but a police spokesman said the men were not "believed to have been involved in the stabbing".

All three are being interviewed by police.