A father-of-five told a jury he never intended hurting his partner's uncle, who suffered fractured ribs and kidney damage.
He suggested the injuries happened accidentally when they both fell on the floor and while he was trying to protect himself.
Fernando Xavier Da Moura (45) denies inflicting grievous bodily harm.
He told Leicester Crown Court he never punched, kicked or kneed 64-year-old Sivan Subiah at any stage, as claimed by the prosecution.
The incident happened as the alleged victim was tending to his terminally-ill mother at her Evington home, on August 20 last year.
Xavier Da Moura (45), had earlier exchanged words with Mr Subiah on the phone. He told the court he accompanied his partner, Mr Subiah's niece, to Evington. Xavier Da Moura said Mr Subiah began shouting at him to leave. He claimed Mr Subiah slapped his face, so he pushed him away.
Xavier Da Moura said his partner mentioned seeing a gun in the house and fearing he would get it, grabbed his shirt to put him on the floor.
He said: "We both tripped. He fell first and I fell on top of him. I didn't think I caused him any injury."
Mr Subiah told the court: "I feared for my life." He disagreed with the defendant's version of events.
The defendant's partner, said to have witnessed the incident, has not given evidence in court. The jury is due to consider the verdict today.