"We were not really good in defending crosses today," he said. "We should not only stop the crosses from coming in, but also keep tight on their men.
"It started well and we scored a goal but eventually things turned sour. We started to get a bit loose [with our marking] and they were quite fast with their breaks, so we couldn't match their speed in those instances.
"It took us a bit too long to settle down but until then everything went well for them and they were up by three goals."
Nonetheless, Selvaraj was of the opinion that it was better for Warriors to be handed such a defeat early on in the season as it gave them time to address their problems.
"It's better to lose awfully now than later," he added. "These are the games that really let me find out where we are going wrong.
"We are definitely not capable of a performance like this. We should reflect on all this, look forward and work harder when we get back in training.
"The players realised where they went wrong, especially on an individual basis, so we should move on."
The Warriors were particularly exposed down the left due to teenage full-back Zakir Samsudin, but by the time he was replaced by Syaiful Iskandar in the 35th minute, the damage had already been done, although his coach was unwilling to single out his youngster for criticism.
"I would say yes," Selvaraj replied when asked if Zakir's inexperience had been exploited. "But he's young and learning.
"He has a lot of potential."