Coach Steve McNamara said England were "distraught" after the World Cup semi-final defeat by New Zealand.Shaun Johnson scored a try with seconds remaining before kicking the decisive conversion as the world champion Kiwis won 20-18 at Wembley Stadium.
"We are bitterly, bitterly disappointed," said McNamara, who is now out of contract.
"The team showed great determination but sport at the very elite level can be cruel."
The host nation built an 8-0 lead but conceded 14 straight points, then battled back to 18-14 up, before Johnson struck with the last play of an absorbing contest.
Ryan Hall could not quite hold on with an attempted intercept, while George Burgess conceded a penalty in the final minute to hand the Kiwis the set from which Johnson scored.
But McNamara said it would be "very cruel to pin the blame on anybody for that result".
Asked specifically about Sinfield, he added: "Kevin has not got anything to blame himself about.
"I cannot speak highly enough of him. If you had a daughter, you would want her to marry someone like him.
"He does the little things when no-one is watching, the sign of a true champion. He is not blessed with outstanding size or power but he gets every ounce out of himself.
"We have got to move on. Right now we are all feeling this, the worst we can probably be, but worse things happen in the world."
McNamara left out Rangi Chase after the half-back had started every other England match at the tournament.
Chase was not at Wembley after McNamara granted the 27-year-old's request to return to his family.
It was a shock selection but McNamara showed during the campaign he was not afraid to make tough decisions, with Gareth Hock leaving the squad days before the World Cup started for disciplinary reasons while fellow forward James Graham was left out of the team for the opening match against Australia.
"We've had some ups and downs," said the England coach. "We've dealt with things when they have come up, maybe some other teams haven't, but we have come through the other side and put in a brilliant performance today."
"For our sport, this World Cup, this occasion and many others during the tournament, are doing tremendous things.
"For young kids from the grassroots who are watching, and dream that one day this could be them, I hope it inspires them.
"I hope the tournament attracts new fans and new sponsors. Our sport needs and deserves that support."
But the coach, who took charge in 2010 after previously serving as assistant, refused to be drawn on his own future.
"No, I'm not sure, it is too early," he said, when asked if he intended to carry on.
"I have been solely focused on trying to give the best preparation towards being successful. It has been a pleasure to put the programme together."
Man of the match Sam Burgess, who scored one of England's three tries, said his side did not get what they deserved from the game.
"I'm very disappointed for the team," said the South Sydney Rabbitohs forward.
"I thought our effort was there. We fought through some patches as a team and showed a lot of strength. I'm thankful for the man-of-the-match award but I'd rather have the win than this medal.
"We put a lot of hard work into this tournament and we feel we've not got what we deserved."