Rhinos were scheduled to face Catalans Dragons in Perpignan this evening, but opted not to go despite the game not officially being postponed.
In a statement, the Rugby Football League said their board would determine “the consequences of this decision on the match, and any sanction”.
Sinfield, though, was defiant and insisted: “I absolutely stand by the club’s decision.”
He said: “I think it was the right one, made in some unprecedented times when some other sports are cancelling fixtures and a lot of clubs are isolating players and closing training grounds.”
The situation changed rapidly after an announcement on Tuesday that – against Catalans’ wishes – the game would take place, but behind closed doors.
On Wednesday, a player sent home from training the previous day due to illness began to feel worse and when he showed full coronavirus symptoms on Thursday, Rhinos began to consider not making the trip. The player was tested for coronavirus, but the result is not yet known.
“We always wanted to play this game,” Sinfield insisted.
“That is why we pushed so hard on Tuesday for it to go ahead, but since Tuesday a lot of circumstances have changed.
“It is a shame and in hindsight we’d love to say the game should have been postponed on Tuesday, but none of us had a crystal ball or knew where we’d end up [yesterday].
“I am really disappointed the game won’t go ahead this weekend and that there’s a lot of fans haven’t been able to travel.
“And I am disappointed there’s a lot of fans already in France and Spain who were looking forward to a game.
“But I would like to assure every single one of them that this decision was made purely on putting our players and staff and the care of them at the heart of it.”
So far, Rhinos’ game at Catalans is the only rugby league fixture called off.
Professional football in this country has effectively been put on hold until next month and Sinfield admitted it is likely rugby league will be similarly affected at some stage.
“That seems to be the direction of travel,” he said.
“I think it probably depends on what happens over the next couple of days and how quickly this escalates and spreads.
“I think the pressure from other sports, as well, may change where we go and what we do.”
Potentially going for weeks without income midway through the season would be a huge blow to clubs at all levels.
Sinfield added: “I do understand the finances behind it all and how difficult it would be for clubs who may lose revenue over this period.
“But I think my counter-argument would be what cost do you put on someone’s life?
“That is exactly the message from our club, we wanted to do the right thing for our players and staff.
“It will be interesting to see what happens over the next day or so, but we have seen a lot of dominoes fall with other sports and clubs making decisions and trying to put their athletes and clubs at the forefront of their care.”
Earlier in the week Catalans wanted to switch the game to Leeds, with the return game in August being played at Perpignan.
They then called for a postponement and Sinfield said he understands why they were disappointed with the decision to press ahead, behind closed doors.
He confirmed Catalans backed Leeds’ option not to travel and revealed: “I spoke to [coach] Steve McNamara [on Thursday night] and he absolutely agreed with our stand on it. This is bigger than sport and a game of rugby and we have absolutely got to the right place. Two clubs have come together and made a smart decision.”