A probe into the 20-year-old's death continues on Tuesday, with Suli set to give evidence more than three years after the emerging talent fell ill during preseason training.
Suli - a Tongan international who now plays for St George Illawarra - is also expected to be joined by NRL players and former teammates Sione Fainu and Ben Trbojevic.
Titmuss suffered a seizure after a cardio workout at the club's base at Narrabeen, on Sydney's northern beaches, on November 23, 2020 and died five hours later in hospital.
Believing his teammate to be relaxing after an intense training session, childhood friend Joshua Schuster told the court on Monday Titmuss had not appeared to struggle throughout the day.
"He was good. He finished the whole session which was normal," Schuster said.
"We were stretching and he was lying on his stomach for like five to 10 minutes then I just had a feeling.
"All the boys left and I went up to him. I was trying to touch him and he wasn't responding.
"He was just lying there. His eyes were closed. Next thing you know, he had a seizure."
While an autopsy was unable to ascertain the cause of death, counsel assisting the coroner Adam Casselden SC told the court Titmuss most likely suffered exertional heat stroke.
Paramedics who arrived at the scene noted Titmuss's temperature was 41.9C, while his heart rate was over 140 beats per minute (bpm).
But coaching staff and medical practitioners did not identify that Titmuss was suffering heat stroke, treating the symptoms of his seizure instead.
Asked whether the NRL were enforcing their heat policy on the club at the time, then Manly chief medical officer Dr Luke Inman told the inquest "they weren't and they don't".
"They recommend a period of acclimatisation in the NRL, but there's no exact way of guiding teams on what that entails," he said.
"What it should mean is a graded increase in exposure to the heat so the body can adjust gradually and build a tolerance to it.
"The first 10-14 days of preseason are the deadliest.
"Those junior athletes should be taking it a little lighter. They should not be performing any max exertion during that period.
"But it wouldn't be done at any NRL club - no one will comply to that in a performance setting.
"They would be feeling that they would be two weeks behind any other team if they put the brakes on."
17°C