"We have said you can't waste a game now and that's what we've done," McClaren told British media after the match.
"We felt we could come here and get a result but we had to come here and perform at our level and there were a lot of players below that level and that is why we lost.
"A few players did not... show their quality which is why we lost. In terms of injuries and performance that is not our level of performance which we have been producing."
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The manager urged his players to react against West Bromwich Albion on Saturday, calling for a return of the attitude that saw the side pick up 11 points in nine games since December, with wins over Liverpool, Tottenham Hotspur and West Ham United.
"We have to dust ourselves down, we have 52,000 people who will turn up at the weekend and demand that, and we have to give them something now against West Brom," McClaren said.
"The attitude has been a different class the last couple of months. We had bad results against Leicester and Crystal Palace (in November) where the attitude was questioned but since then it has been excellent.
"I felt it was disappointing we returned to that level and that is unacceptable."
(Reporting by Simon Jennings in Bengaluru; Editing by John O'Brien)
