Lerena was the first witness in the globally watched trial, which started Monday, to allow himself to be broadcast on television under a judge's order allowing cameras into the courtroom but preserving the right of some witnesses not to be shown. The boxer wore a suit and leaned forward with an intent expression as he answered lawyers' questions.
His testimony about the restaurant shooting was a reminder of how 27-year-old Pistorius, who ran for South Africa in the 2012 Olympics, once commanded respect among his peers. The boxer described Pistorius as "an icon and a legend in sport" and said he sought advice from the runner about diet and running.
The episode occurred during a busy lunchtime at Tashas restaurant in the swank Melrose Arch area of Johannesburg in January 2013, and relates to three firearms-related charges against Pistorius, in addition to the murder charge. Pistorius pleaded not guilty to all four charges.
One friend, Darren Fresco, passed his gun to Pistorius under the table and told him that there was a bullet in the chamber, Lerena said. Then a shot went off, puncturing the floor near Lerena's foot, he said.
"There was just complete silence," said Lerena, who described being in shock and having blood where his toe was grazed in the incident. Then, he said, Pistorius apologized, saying: "Are you OK? Is everybody OK?"
Before the restaurant management approached the table, Lerena said, Pistorius asked Fresco to say he was responsible for the gunshot.
Lerena said they paid the bill and left the restaurant and he never spoke about the incident. Two days after Pistorius shot Steenkamp, he said, he woke up to find over 100 missed calls on his telephone as media from around the world tried to contact him to ask about the gun incident.
Chief defense lawyer Barry Roux attempted to establish it was noisy in the restaurant, which the manager testified was full with over 200 customers, and that Pistorius did not hear Fresco say the gun was "one-up" or that there was a bullet in the chamber when he passed it.
But Lerena's testimony that Pistorius asked a friend to "take the rap" wasn't challenged.
"He did say, 'Fresco, take the blame because this could be big,'" Lerena said in court.
The wife of the restaurant manager also said in her brief testimony that the shot went off near to where a child was sitting.
Earlier Wednesday, Roux sought to undermine the prosecution testimony of a couple who say they heard a woman's screams and gunfire the night that Pistorius killed Steenkamp. Telephone records will show that the banging sounds the neighbors heard were not gunshots but a distressed Pistorius breaking down the toilet door with a cricket bat after realizing he had shot Steenkamp when she was in the toilet, thinking it was an intruder, Roux asserted.
Throwing doubt on the witnesses' recollection of the sequence in the early hours is crucial for Pistorius' defense after the state maintained there was a loud argument on the night he shot Steenkamp through a door in his bathroom and the screams and shouts were before a gun was fired.
The runner's defense team wants to show the screams were Pistorius calling for help after the accidental killing and before he used the bat on the door.
Pistorius was born without fibula bones because of a congenital defect and his legs were amputated when he was 11 months old. He ran on carbon-fiber blades and is a multiple Paralympic medalist. He also competed at the London Olympics but didn't win a medal.