The club reportedly spent over 50 million pounds to bring in five new players to the squad, four of them to strengthen the attack, but they are the lowest scoring club in the league having scored just three goals so far.
"Everybody has to look at themselves in the mirror and ask if they gave everything," Krul told the club's website after the 1-0 loss to Sheffield Wednesday.
"If not, they have to start straight away, because what we are doing at the moment is really not good enough."
The keeper blamed lack of confidence for Newcastle's sorry performance and said the team's attack needed to do more.
"You have to be honest enough to say that we are getting up there and playing some good stuff to get there, but it's all about the final quality in the final third, which just isn't happening," the 27-year-old said.
"I'm not just blaming the forward though because we need to look at the whole team. Defensively we haven't been on top form yet -- nobody has been.
"Everybody needs to grow now. We need to come out and show we are real men."
Manager Steve McClaren has called the start to the season a "bit like a car crash" and conceded the club are "close to a crisis".
The fans will hope to avoid a repeat of last season, where they failed to record a win in their first eight games and needed a victory over West Ham on the final day to ensure their Premier League survival.
The club, who will be without key defender Steven Taylor after he was ruled out for eight weeks, welcome champions Chelsea on Saturday and travel to face current leaders Manchester City the following weekend.
Newcastle have, however, won their last three home league matches against Chelsea while their manager Jose Mourinho has never won a league match at St James' Park in his five visits.
Krul has called on the supporters to be their 12th man on Saturday.
"Chelsea and Manchester City are two massive games and we have to show that we've got the fight for it," Krul said.
"We have to try and turn it around on Saturday against Chelsea, with 50,000 Geordies being that extra man that we really need right now."
(Reporting by Shravanth Vijayakumar in Bengaluru; editing by Sudipto Ganguly)
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