But he says the Jets have already passed one major test: playing "really poor football" but still winning.
It's the mark of any championship team, and one Newcastle displayed on Saturday as they came from behind to beat Adelaide United 2-1 at Coopers Stadium.
The result put them on top of the A-League ladder but the performance didn't please Merrick one bit.
"There's definitely positives to take out of the game because we've now got a team that are very resilient and can go a goal down and not just draw but get a win," he said on Tuesday.
"(But) if we keep performing like that we're not going to win many games."
Merrick said the Sky Blues were at a "different level altogether" compared to Adelaide.
He described their shock loss to Central Coast last week as proof the A-League's quality chasm was closing.
"There's no doubt that teams are all improving. The lower teams have recruited well, they're coached well," Merrick said.
"There's a closing of the gap occurring. But it's very hard to go through a whole season and not concede any games. Everyone's going to lose games, ourselves included.
"It's a case of bouncing back and there's no doubt Sydney will want to bounce back this weekend against us."
However, Merrick quickly hosed down suggestions a win over Sydney would prove the Jets were the real deal.
"I try not to place that much emphasis on one game," he said.
"It all comes down to consistency over a period of time and to be fair to the boys, we've had a bad game.
"We've still won the game, showing our strength of character. And we have to take that as a lesson to be learned."
The Jets are one of only two unbeaten sides in the A-League - the other is Western Sydney, who have won only one match and drawn five others.
Meanwhile, Merrick said he won't look at strengthening his squad, or replacing injured marquee star Ronald Vargas, until the January transfer window opens.
"Some overseas clubs will want to offload players that are not getting a game - some of them are very good players, and we'll keep an eye on that January window," he said.