Duran’s goal made it 1-1 at the Estadio Algarve, but Sporting scored three times in the closing stages for a comfortable victory.
O’Neill also fielded several youngsters in the second half and the Northern Irishman was pleased despite the result against last season’s Champions League quarter-finalists.
“First of all, it’s a great experience for some of the young boys to be playing against a side like that,” he said. “But secondly, and the senior players too, we all can learn from it.
“Learn just fundamental things – closing players down, trying to get there first, recovering quicker, things like that.
“But that’s all part of pre-season. I’ve been here before so many times. Sometimes you get carried away with pre-season results if things have gone well and vice versa in many aspects.”
Champions Celtic have two more friendlies this month, against Middlesbrough and AC Milan, before they return to competitive action against Dundee in the Scottish Premiership on 3 August.
