Frank Lampard believes the next step for his youthful Chelsea side is to sustain their performance levels across the full 90 minutes of matches.
Chelsea picked up their fifth Premier League win in a row on Saturday with a nervy 2-1 victory against bottom of the table Watford at Vicarage Road.
The Blues looked comfortable after opening up a two-goal lead through Tammy Abraham and Christian Pulisic, only for Gerard Deulofeu to pull one back from the penalty spot 10 minutes from time.
And if not for a last-second save from Kepa Arrizabalaga to deny fellow goalkeeper Ben Foster the home side would have snatched a point, which Lampard admits is an area of concern.
"At times we are certainly producing some of the form that I want from us," he said.
"Our work off the ball in some games where we have been pushed hard, like Ajax away and Liverpool, has really pleased me.
"They have worked on that in training to a level where they are fit enough. In periods of games I am pleased with the way we combine and switch the ball. If I've got a gripe it is that we are not sustaining that for long enough at a time."
Chelsea also conceded twice in the final stages of last week's 4-2 win at Burnley and Lampard added: "Maybe it's football. Liverpool go away [to Aston Villa] and are behind for long periods, Manchester City, too.
"So maybe I'm being a bit demanding. You have to respect the opponents. It is not always as easy as it appears and football will always be a work in progress.
"We have young players who have been out on loan who have come in and are working with senior players, so things will always take time to get where you want them to get to."
Chelsea's players were aggrieved with referee Anthony Taylor's decision to award a penalty following a lengthy VAR review after Jorginho was adjudged to have fouled Deulofeu.
Captain Cesar Azpilicueta is unsure if the technology is being used in the correct manner and wants referees to make more use of pitchside monitors.
"We have a lot of meetings about the VAR," he said. "There is a screen on the pitch for the ref to look and see why he made the decision not to whistle for a penalty.
"We are not using the system in the right way, which is something to help the referees make the right decision. They are human, the same as players.
"We make mistakes but why not use the whole system in the right way? That's my big point in this case and in other cases that we have seen. It could help."