The Premier League champions took a 2-0 lead into the half-time break, but found themselves 3-2 down in the dying minutes, only for Ashley Young to rescue his side with a last minute equaliser.
The Scottish coach was clearly unhappy with not picking up the three points, especially after being in such a dominant position.
“I think we were careless,” he told Sky Sports.
“They made three or four openings in the first half and the lack of concentration cost us. We threw the game away. [I told the players] to finish the game off because of the opportunities they created in the first-half.
“It’s a wake-up call, in many ways. But, to lose three goals at home, the defence and midfield need to be better than that in terms of concentration. If you lapse, the quality in the Champions League can make you suffer,” he stated.
Antonio Valencia was penalised for a foul on Marco Streller, gifting the Swiss side a penalty in the second half, but Ferguson has questioned this decision.
“I don’t think it was a penalty,” he said. “You can see quite clearly that Valencia won the ball. It’s a poor decision as far as I’m concerned.
“But there’s a great character at this club and it showed again tonight,” he concluded.
United now host Norwich at Old Trafford on Saturday, but will be concerned that their form in Europe does not match their excellent domestic start.
FREE football app that pays you for viewing ads