Perth Glory coach Richard Garcia says inexperience and fatigue have been the root cause of his team's late fadeouts during the Asian Champions League.

Glory's youth-laden squad has put in brave efforts in each of their three games during the rebooted ACL, but are yet to come away with anything to show for it.

Their two games against Korean powerhouse Ulsan Hyundai this week proved to be the most heartbreaking.

On Tuesday, Glory led 1-0 before conceding goals in the 89th and 93rd minutes on the way to a 2-1 loss.

In Friday's rematch, Glory were on track to secure a point before conceding goals in the 87th and 89th minutes in a 2-0 loss.

Glory fielded teams littered with youth on both occasions, with the lack of a proper pre-season preparation also proving significant in the late fadeouts.

Garcia said once the pressure ramped up late in Friday's game, his players struggled to match it.

"Towards the back end of the game there wasn't much experience on the pitch at all," Garcia said.

"Eventually we gave away a silly goal from our free kick and then copped another.

"That little bit of fatigue has set in now that the games are coming thick and fast and that concentration for the whole 90 minutes-plus needs to be there.

"That's something that you need to work on in pre-season."

Spanish star Diego Castro was rested from Friday's match, but he's expected to return for Monday's clash with Shanghai Shenhua.

Glory sit bottom of Group F and are no chance of progressing, meaning Garcia can use the final two games to experiment and prepare his group for the A-League season.

The game against Shanghai is followed three days later by a clash with FC Tokyo where Garcia is set to heavily rotate his squad.

"We need to be mindful of people's loads and make sure we don't break them," Garcia said.

"We've still got another two games to play here and we need to come out unscathed."