The team fought back from 4-2 down with only eight minutes remaining to level as Andros Townsend converted a penalty (85 minutes) before drilling home for 4-4 with only two minutes left.
But having climbed that mountain, they were knocked down again as Chelsea grabbed a 5-4 victory in the fourth minute of added time.
Earlier, Tammy Abraham put Chelsea 1-0 up (18 minutes), Shaq Coulthirst levelled (21) only for Fikayo Tomori (23) and Kasey Palmer (48) to take the visitors into a 3-1 lead.
Coulthirst added his second for 3-2 (72), Jay DaSilva (82) restored the two-goal advantage and then the late rally as Townsend's double made it 4-4. As we entered the final minute of added time, we failed to clear Fankaty Dabo's free-kick and Jake Clarke-Salter fired home the winner.
"The disappointment is that having got out of jail and fighting back from 4-2 to 4-4 with two minutes to go, we didn't manage the game better at that point," reflected Ugo. "And once again, it showed the importance of defending set-pieces and concentration.
"There was enthusiasm, spirit and hard work but goals change games and when you look at the facts in black and white, we've conceded five goals at home - or we've scored four goals at home and still lost the game.
"It was devastating for the players after the way they hauled themselves back into it to then lose in injury time.
"The winning goal comes from a set-piece and that's the disappointment. We've got to do our jobs when that free-kick comes in but we didn't do well enough and we lost to the last kick of the game.
"But we have to take heart with the way we came back because at 4-2 and 82 minutes on the clock, the game was dead.
"We go again now. We've another big game against City next Monday and it's an opportunity to put this right."