Adam Le Fondre scored what appeared to be a mere consolation for the Royals with a smart left-footed finish past Ross Turnbull with three minutes remaining.
But there was still time for the Reading striker to score his fifth goal in three Premier League games, with Le Fondre ideally placed to capitalise on a scramble in the Chelsea area deep into added time.
“The atmosphere was not good in the dressing room. We did everything to win the game,” Benítez told BBC Sport.
“For 85 minutes we were dominating everything. By the end a free-kick cost us. We created enough chances to score four or five goals. It is very difficult to take.”
Reading manager McDermott heaped praise on his star substitute, whose brace held the Champions League winners to a draw and moved the Royals out of the bottom three.
“You might not have seen that coming, but we have done it here before,” said McDermott.
“If you have got Adam Le Fondre at your club, you always have a chance. We have faith, drive and a determination to keep going.”