'It was a lack of concentration that killed us downright carelessness,' said the Manchester United manager.
'We threw the game away. I warned the players at half-time that Basle had created two or three clear openings and needed finishing off, but it made no difference. Our defenders and midfielders have to do better than that.
Frustrated: Sir Alex Ferguson rued the costly errors
'We were left grappling at the end to salvage a point, and losing a two-goal lead at home like that is a wake-up call.'
Ferguson admitted that complacency may have played a part, adding: 'Too many players were playing far too far forward. They seemed to think they could do that against a side like Basle, even though they had been prepared properly.'
Ferguson was unhappy with Italian referee Paolo Tagliavento, saying: 'It was a poor decision to award them a penalty, because (Antonio) Valencia won the ball. Not only that, the referee kept getting in the road.
'Every time we passed the ball, he was in the way. I think he wanted to play.
Dispute: Ferguson claims Valencia won the ball as Frei scores the penalty (below)
'At least we showed great character to rescue a point, but our concentration levels have to be better.'
Ferguson said his defence still should have had enough experience to cope with Basle even with 19-year-old Phil Jones in central defence but admitted they are suffering from inconsistency.
Mixed feelings: Welbeck was pleased with his goals, but disappointed to draw
'There is still enough quality in the back positions - Evra and Ferdinand are very experienced. But you always like to have a back four playing consistently and we don't have that at the moment.
'It is not a problem for us because of the quality we have in the forward positions guarantees us goals, and we really should have put that to bed tonight in the first half.
Ferguson did praise Welbeck's contribution, saying the 20-year-old 'did very well' in the first half but had tired in the second.
And Welbeck himself admitted it 'felt like a defeat', despite Ashley Young's last-minute point-saver.
'We should have put the game away,' said Welbeck. 'It's just not like us. I'm over the moon with two goals, but it's a team game and I'm disappointed with the result.'
Old Trafford match zone: Fergie gets his point across to BerbaManchester United 3 Basle 3: Young's late show saves Sir Alex's blushesRevealed! The soft side of Sir Alex, United boss has turned off the hairdryerCHAMPIONS LEAGUE LIVE: Manchester United 3 Basle 3 as it happenedAll the latest Manchester United news, features and opinion