Manly's 36-16 defeat to Newcastle was riddled with poor handling and leaky defence, before being booed off by small sections of the Brookvale crowd on Sunday.
Seibold's men made 15 handling errors for the afternoon, with the nightmare starting when Luke Brooks let the opening kick off go dead before Newcastle scored in the next set.
Brooks spilled another kick off, with that ultimately killing off any chance of a second-half comeback at 30-16 down when the Knights again scored net set.
Manly's day was best summed up by a Reuben Garrick linebreak late in the match, with no teammate looming in support play or even getting to the subsequent play-the-ball.
Making matters more frustrating for Manly will be the fact they could not capitalise on Newcastle losing Dylan Brown and Kalyn Ponga to injury in the first half.
The Sea Eagles have a bye next week before Daly Cherry-Evans returns to Brookvale with the Sydney Roosters in round four, in what now becomes an early crunch game for Manly's season.
The start to the season had always loomed as crucial given a run of three straight home games, with Manly's record at Brookvale far superior to on the road in recent years.
But Seibold pointed to his first year as an NRL coach at South Sydney as proof the situation could be rectified, with the Rabbitohs recovering from 0-2 to make the top four that year.
"Of course we would have loved to have won both our first games, but it's not fatal," Seibold said.
"One thing we won't do is panic or change our schedule. We're very well prepared and well planned.
"I've been zero-and-two before and been a top four side as a coach.
"The really good teams in the competition win at 60 per cent, the good teams win at 50 per cent, and so there's another 22 games to go.
"We need to show far more improvement than what we showed today. But I've got a lot of faith in the group. That doesn't change."
Seibold had faced scrutiny on his future as Manly coach midway through last year, before holding onto his job with the Sea Eagles finishing with a 12-12 record.
Manly had looked somewhat better in last week's golden-point loss to Canberra, albeit while giving up a 14-point lead before then coming from 14 behind to force extra time.
"Our ability to then show resolve off the back of (errors) is what we're searching for," Seibold said.
"We showed signs of that last week. Clearly (Sunday) afternoon we didn't."
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