Slaven Bilic believes his high-flying West Ham side are still capable of improving in "every aspect" of their play.
The Croat, who replaced Sam Allardyce as manager in the summer, has guided the club to third in the Premier League, claiming the scalps of Chelsea, Arsenal, Liverpool and Manchester City along the way.
West Ham visit Premier League newcomers Watford on Saturday and Bilic is confident his side can maintain their impressive form as the season wears on.
"It has been a good start and we are enjoying it but we are on the ground totally," he said. "It is only a start but we are confident, we are playing well and if we continue to work hard as we have since day one, of course there will be ups and downs results-wise, but I don't see a reason why we should drop dramatically.
"The core of the team has been playing together for some time now and that is the greatest thing, we only added some players we thought were necessary to make the team better.
"It is still early days to say where the limits are for this team - what is definite is that we have lots of room to improve from every aspect. Some players know each other only for a couple of months so we can improve organisation and transition.
"We can improve small things like set-pieces and second balls. We definitely have to improve in shooting because we are not shooting enough. That doesn't mean I'm not happy with the performances so far but we can improve in absolutely everything."
Club-record signing Andy Carroll came off the bench to head the winner in last weekend's 2-1 win over Chelsea while fellow striker Enner Valencia is also closing in on a return to action.
Bilic admits he has some difficult decisions to make over team selection in the coming weeks and hopes to keep his squad fit for a tricky run of fixtures, which sees them host Everton and visit Tottenham in the next three games.
"Now I have a positive headache," he added. "I have many good players who deserve to be selected in the first 11 or the 18 but I have to make the choice.
"We have most of the players back and I'm glad of it, our medical team has done really well. We are planning that if someone is tired he will get individual training and stay in the gym to protect them from injuries."
And he knows Watford will provide a stern test as he is a big fan of manager Quique Sanchez Flores.
"I rate Quique really highly," added Bilic. "Not only because of his past - he did it as a player and a coach at big clubs - but to do it here and make a team out of 20 new players in such a short time is amazing and they look very, very organised.
"He won the Europa League with Atletico Madrid, it doesn't surprise me at all.
"He is a great coach, he has got the most nationalities in the team and to make them look like a team that has been playing together for three or four years, it is a great job."