NEIL Harris felt his side should have prevented all three of CD Tondela's goals as Millwall lost for the first time in pre-season.
The Lions came back to level twice against the Portuguese side before Luis Machado scored the winner in the 67th minute.
"I think first and foremost we're disappointed with losing," Harris said. "It's pre-season, but of course results matter.
"I hate losing. I want us to have a winning mentality.
"I'm pleased with lots of aspects of the performance but disappointed with how the game went, the stoppages in play, the falling over and the silly fouls.
"That was disappointing because we never got into a rhythm in the second half. I was delighted with the two goals we scored but there were another couple of chances we should have taken.
"I think all three goals were avoidable. The first one was our own throw-in. We gave the ball away and then conceded a needless free-kick 30 yards from goal.
"The second one was a good finish but we could have defended that slightly better as well. We could have prevented the ball ending up in our box, 16 yards from our goal.
"The third one also was avoidable, albeit it was a fantastic delivery onto the boy's head.
"But let's not forget we were playing against an extremely talented, technical side that are playing in the Portuguese top division.
"Their use of the ball was really good at times, especially in tight areas.
"But I would certainly expect us to defend better next week."
Harris said that he was pleased with the attacking intent his side showed, singling out Fred Onyedinma for special praise.
The 18-year-old started on the right wing and showed maturity and skill to lift the ball over Matt Jones for Millwall's first equaliser on 14 minutes after Lee Martin had driven at the heart of the away defence.
"It was a fantastic finish from the young man," Harris enthused. "I thought he was outstanding all game – with and without the ball, it's important to say.
"I think he showed everybody what he's all about and what they're going to see plenty of this year. The build-up to his goal was excellent from a counterattack.
"I think the counterattack for the second goal was just as good, with Fred and John (Marquis) drawing the foul when it looked like John would have been through for a shot.
"But we put the ball in the box – and I've spoken about set plays being vital to us – so obviously the second goal was pleasing from that aspect.
"And I think some of the forward runs to get into good positions from our front four players was really excellent.
"John could have had a couple of goals on another day, but I thought some of our play going forward was really good."