The 34-year-old victim was taken to hospital in a critical condition following the attack in Upper High Street at around 12.15pm on Tuesday. Police believe he was deliberately targeted.
A 38-year-old man suspected of being the attacker handed himself in at a police station around two hours later and has been arrested on suspicion of attempted murder.
Witnesses heard screaming as the victim, who works at easy4insurance on Upper High Street, was attacked outside Trendy Carpets and Flooring.
The man was treated by two off-duty medics until emergency services arrived while his attacker is believed to have made off in a van.
An air ambulance landed and the street was cordoned off as a number of police cars and ambulances descended on the scene.
Muhammad Ahmed, who runs A1 Hair Studio on Upper High Street, saw the knifeman run away from the scene.
He said: "We heard screaming and a voice and then we went outside and he started stabbing the guy. I saw the guy run who was attacking ran away and the other guy was lying down next to the shop there."
Meanwhile Rafaket Khan, who runs the nearby Ghosa Foodstore, recognised the victim as a regular customer.
He said: "He is a really humble bloke, I can vouch for this kid - every morning I open up and he comes in and usually buys a drink.
"He is the type of guy where even if he only had five minutes and there was someone else behind him, he would move back and let them be served first - he is a really nice guy.
"It hurts knowing that this has happened because he would never hurt a fly, he is really kind and a really really nice guy."
The road remained cordoned off from easy4insurance to the Lamp Inn three hours after the stabbing as police started their investigation.
Detective Inspector Jackie Nicholson, said: “This is a shocking incident in which a man has been attacked in the street in broad daylight.
“Our enquiries are at an early stage but we’ve already seized CCTV and spoken to some key witnesses; at this stage we believe this to be a targeted attack.
“We’re still appealing for witnesses and would ask anyone who saw what happened to please get in touch as they would have important information.”
Claire Brown, spokeswoman for West Midlands Ambulance Service, said: "Two off-duty ambulance staff together with student paramedics and ambulance training tutors came across the incident and stopped to render aid to the man who had been injured.
"Three ambulances, a paramedic officer, a critical care paramedic and the Midlands Air Ambulance from Strensham with a MERIT trauma doctor and critical care paramedic on board were sent to the scene.
"The man sustained serious injuries after reportedly been stabbed and received advanced trauma care by the team of medics at the scene before being conveyed land ambulance on blue lights to hospital where, on arrival, his condition was described as critical."
Anyone with information is asked to contact police online or on 101 quoting log 1871 from June 8.