The jury was this morning shown a police interview with the coach after he was arrested for sexually assaulting a young person in 2015.
McGrath said he'd known the boy for many years as his coach and was at a loss about the allegations.
The Crown says during the course of the investigation another boy was interviewed and also said McGrath sexually assaulted him in 2013.
Earlier, the court heard a specialist police interview with the boy, now 16, who alleged McGrath called him into the changing rooms when he was 13 or 14 years old to discuss him not making the Under-14s team.
The boy said the coach told him it was because he wasn't mature like the other boys, physically or mentally.
The boy claims McGrath then sexually violated him.
The boy said in the interview that McGrath told him: "I apologise if what I just did disturbed you or what we just did offended you", then started talking about the rugby match.
"I knew it was wrong but I had too much trust. I knew him since I was 10."
He said McGrath hugged him and told him: "Don't tell anyone about this. This can be our little secret."
THAT'S A MEAN ACCUSATION
In McGrath's police interview, he was asked by the officer in charge, Detective Dean Taylor, about whether he'd ever spoken to the boy about lacking maturity.
"No, I don't think so because I think he's a gifted player. I think he's ahead on the other players in the school ... he's going to be a good boy."
When Taylor detailed the allegations against him regarding that incident, McGrath told the detective: "That's a mean accusation that. It's ugly."
Taylor then asked about an earlier incident when the boy alleged McGrath had instructed him to masturbate in front of him.
"Can you explain that?" the police detective asked.
"That's mean. That's ugly."
Taylor asked whether he had anything else to say about the sexual allegations against him.
McGrath said he had "huge respect for that boy".
"But I have to say I don't believe it."
He was also asked about a time the boy was injured during a game and the teen alleged McGrath rubbed his genitals with a soap-like substance.
McGrath said he asked if it was "okay to rub it" to get the bruise "off the bone".
He said he used a soapy moisturiser because there was no Vicks rub or Deep Heat in the changing rooms, but the door was open the whole time and the boy's mother wasn't far away.
The coach told the detective he'd talked to the boy and his brother about their hygiene at their mother's request and instructed them how to wash their penises.
McGrath said the boy was a "perfect" player who had a bright future in rugby.
"He floats like a bumblebee, that boy, or a butterfly."
The boy gave evidence via and audio-visual link on Tuesday and under cross-examination defence lawyer Siobhan Buckley told him McGrath didn't accept the allegations.
The boy denied lying.
EMBARASSED TO TELL MY PARENTS
The other boy alleges McGrath showed him how to masturbate and told him it would relieve stress before games.
The jury was shown the specialist police interview with the boy in which he said in 2013 he and McGrath's nephew were trying to lose weight to get into a team.
After a training session, he said the coach told them to strip off and weigh themselves in the club's trophy room.
McGrath's nephew went first, then left the other two alone.
The boy said McGrath then stripped his bottoms and underwear off before weighing himself then asked if he masturbated.
The boy said he didn't and said McGrath told him:
"You can do it in the shower whenever. He told me it was to relieve stress and stuff like that."
The coach then allegedly masturbated for "about two seconds" and told him to do the same, which the boy said he did so he "could get out of there".
"I kind of trusted him but once he did it, it wasn't really that big of a deal to me because sometimes he tries to act like one of the boys, one of my friends. So he swears sometimes when he's angry and stuff like that."
The boy said the first adult he told was the detective investigating the other allegations in 2015 because he didn't want to worry his parents.
"I was kind of embarrassed about it to be honest, I didn't want to tell my parents about it especially because I didn't want them to think I'm weird."
The boy is being cross-examined by defence lawyer Julie-Anne Kincade at the trial which will continue this afternoon.
