Luiz Felipe Scolari admitted his side gifted Roma a 3-1 Champions League win, but insists Chelsea are still in a good position to progress.
Former Blues defender Christian Panucci nipped in unmarked to put the Serie A side ahead after 34 minutes, before two strikes from striker Mirko Vucinic put the home side three goals to the good.
John Terry grabbed a consolation for Chelsea, who had Deco harshly sent off for a second yellow card nine minutes from time.
Victory would have all but ensured Scolari's side progressed from Group A, but the Brazilian conceded they were off colour.
"We gave too many opportunities to Roma," he told ITV4.
"We made too many mistakes, made wrong passes and had bad positions.
"[For the] first goal there was not any player covering him (Panucci) when they crossed. After this, we were anxious and gave more opportunities.
"It's okay, all of the groups are difficult. We lost one game here and there are other team arriving behind us.
"If we draw today we are in good condition but we did not play very well and it was impossible to draw or win.
"We now have two chances to win against Bordeaux and Cluj. We'll try."
Roma coach Luciano Spalletti hailed the battling spirit of his players after a win which leaves them second in the group, level on six points with Bordeaux, one behind Chelsea.
"It's a result that gives us a breather and some calmness," Spalletti said. "My players have been exceptional.
"They have shown a great spirit that we had not shown for sometime. This is an important win for us and we deserved it."
Roma went into the game on the back of five consecutive defeats but showed a determination to return to winning ways.
"My players followed my tactics today, something which they had not done in recent games," Spalletti said.
"Vucinic struck two great goals but I have to compliment all of my players because they did a great job."