"Some of the criticism that Issac's received is fair but what's not fair is questioning his commitment to the club.
Listen: Andrew McFadden talks to Martin Devlin
"As far as Issac's form goes, I know there's been some criticism around that and probably fair as well.
"When he came back here in January, he had a short preparation like all the Kiwis did, he probably wasn't in the shape he needed to be in.
"I'm not happy with the way he's playing at the moment. Issac's not happy with the way he's playing, and he's frustrated.
"And maybe that's where that boiled over into yesterday's interview."
He went on to clarify that Luke had been preoccupied and distracted for much of the past month following the recent birth of his baby daughter, after complications forced her to remain in hospital up until last week.
At the same time, calf and knee injuries had impacted on his ability to train and play to the standard expected of him, and despite McFadden offering him the option of taking compassionate leave, Luke insisted he play in the round two defeat against Brisbane.
The following week, a training accident at the team's captain's run saw Luke ruled out of the Warriors first home game against Melbourne with a knee injury, but he returned to play in Monday's morale-boosting win over Newcastle.
"About three weeks ago when his wife gave birth there were some complications with their child and she was sick for quite a while.
"I left it in Issac's hands. I certainly was willing to give him time off but he insisted he play at that time.
"It was an unbelievable sacrifice to make, I certainly couldn't have done that in that situation, so to question his commitment to the club is completely unacceptable as well.
"I've got the confidence and trust that with his class he'll come good."