United were beaten 1-0 by the ASEAN Allstars and were booed off by the home fans at fulltime.
But Amorim says he was happy with the young players who featured, including Sekou Kone, Jim Thwaites and Jaydan Kamason.
He stated, "We were expecting a good game, an intense game, in these conditions. But the good thing is that we didn't have injuries and we saw the young kids.
"The important thing is no injuries, with this weather and everything that we did to arrive here in this day. But, again, it's not an excuse. We should perform better.
"We have to control the minutes of everybody. He (Kone) will play more in the next game on Friday. He did quite well but all the young kids tried, that is the most important thing. They want to play more but we have to rotate everybody, so everybody can play. They did well."