Three weeks ago, the Mariners lost 5-0 at home to Japanese club Kawasaki Frontale but Simon says that result should not used when rating the teams.
"Sitting at the top of the grandstand watching the game, I believe five mistakes from ourselves gave them five goals," Simon told Goal.com.
"I don't think they were a five-goal better team than us; I was confident that with a game plan in Kawasaki we could match them."
In the return match in Japan, the Mariners were much-improved but eventually lost 2-1 due to a late Kawasaki goal, a result that did not reflect the visitors performance.
"It's pretty devastating to not get anything from the game, considering the 5-0 defeat a couple of weeks before," Simon added.
"I thought we stuck to our game plan quite well and coming back from that 5-0 defeat and to not get anything from a game we deserved was pretty devastating in the end.
"No, I don't think [there is a gulf in class].
"They obviously have big budgets at their clubs and we're nowhere near that but I think we showed going into the second match that we can match it these teams.
"They train every day and so do we as well; we get paid a salary and that's just the way football is in Australia."