"It's very much the same kind of combination that we had with the Boks but I have to rate them both very highly." said Smal, who was assistant coach to Jake White when South Africa won the Tri Nations in 2004 and the World Cup three years later.
Having impressed so far for Ireland in this year's Six Nations, O'Connell and O'Callgahan could well come face-to-face with Matfield and Botha when the Lions take on the Boks on June 20, 27 and July 4 in Durban, Pretoria and Johannesburg respectively.
The Munster duo wore the No4 and No5 shirts in both the second and third Lions Tests in New Zealand in 2005 and Smal believes they have what it takes to help the Lions be successful later this summer.
"Paul O'Connell is a machine," said Smal, who represented the Springboks as a player in the late 1980s.
"I rate him very highly - (he is) definitely one of the best locks in world rugby.
"Donncha is very much like Bakkies. He's the grafter, does the dirty work. Not a lot of people see the amount of work he puts in, cleaning rucks, making turnovers.
"Now and then he does get the opportunity to carry ball, and he give us a bit of forward momentum."