The Toffees have impressed in their opening two Barclays Premier League games but they twice surrendered leads to draw 2-2 with both Leicester and Arsenal.
Martinez knows the punishment for any mishaps could be even more severe as the title favourites visit Goodison Park on Saturday evening.
Martinez said: "We know it is going to be a difficult test, but we feel hurt about the points we have dropped so late and everything is down to us to try to be as good as we can.
"But unless you are at your top level you can't really compete against teams like Chelsea.
"It is clear Chelsea and Manchester City have started really strongly. They have shown they have no stopping period, they have just started where they left off.
"They are looking in top form straight away and it could be a really difficult sign for everyone else.
"We know how they played last season and now they have got more flair and more options in attack. That makes them a very complete team."
Martinez guided Everton to fifth in his first season in charge and expects to be challenging at the top end again.
He has seen plenty of positive signs but knows his team need to sustain their stronger spells.
This was highlighted last weekend as they allowed Arsenal to come back from 2-0 down with seven minutes remaining.
Martinez said: "It has been very curious (so far). We have shown incredible signs of the team that we can be.
"We need to extend the first 45-minute performance for 90 minutes.
"When we do that I think we are going to see the potential of the squad."
Martinez will check on the fitness of his two former Chelsea strikers before deciding if he can unleash them on their old club.
Samuel Eto'o, released by Chelsea at the end of last season, this week joined the Merseysiders on a two-year contract.
A lack of match fitness might make him an unlikely starter while Romelu Lukaku, whose successful loan from Stamford Bridge was made permanent for £28million this summer, has a toe injury.
Both players could have reason for wanting to prove a point to former boss Jose Mourinho, although Eto'o this week attempted to draw a line under his dispute with the Portuguese.
Last season Mourinho irritated Eto'o, now 33, by making disparaging remarks about the player's age.
Lukaku was given little opportunity by Mourinho but Martinez does not think the Belgian would have any added motivation.
Martinez said: "I think Rom has found a very strong inner motivation - I don't think he is motivated by who he is facing.
"I think it has been more about his role and status at Everton.
"He is a vital player for us and I think he is enjoying that. He has embraced it.
"I feel we are going to see the best of Rom this season. We are really excited about his performances in all competitions - not because he is facing a former club."