Peter Reid felt his players had let everyone down after Leeds finished bottom of the Dublin Tournament.
Leeds' disappointing pre-season continued as they once again failed to record a victory, losing to a penalty shoot-out to Aston Villa and then going down 2-0 to Eircom League leaders Shelbourne.
"Football sometimes is about attitude and certainly as a team the attitude wasn't right," said Reid on www.lufc.com.
"We had a chat before we went out about Villa being a Premiership side and being up for it, but this was a different type of game where we had to go out and match them and then play our football.
"We got a goal against us and we just fell apart, I know it's a team that we made a lot of changes to. There was enough experience out there to deal with it, but we didn't do that."
Reid also felt the players had not done the Leeds fans justice, who had travelled not only from England, but all over the Republic of Ireland and Northern Ireland to watch their heroes in action.
He added: "When I look at us when we concede a goal, heads go down instead of getting a reaction.
"Against Villa we fought back and showed a lot of character, but on Sunday it just looked as if it was too hot out there and the attitude wasn't right.
"The players did not do themselves justice and the crowd justice because there were a lot of fans here who paid good money to be here."
Gerard Rowe put Shels ahead after just seven minutes and Stuart Byrne doubled his side's tally on 22 minutes.
It could have been worse for Reid's men, but Jason Byrne saw his effort ruled offside on the hour.
Substitute James Milner went closest for Leeds, who will have to show much more when they kick-off the new Barclaycard Premiership season against Newcastle on Sunday.