London, September 29: Christian Pulisic admitted he is "very frustrated" with his lack of playing time under Frank Lampard at the Premier League giants.
Pulisic, 21, was an unused substitute in Chelsea's 2-0 Premier League win over Brighton and Hove Albion on Saturday.
Pulisic moved to Chelsea from Bundesliga runners-up Borussia Dortmund in the off-season amid plenty of hype following a £58million transfer.
However, the United States international has only appeared in one of the club's last five matches – the 7-1 EFL Cup rout of Grimsby Town on Wednesday (September 25).
"Yeah, of course, it is very frustrating, but I will continue to work my hardest because I want to play," Pulisic told NBC Sports after Saturday's game.
Asked if he has received advice from head coach Lampard, Pulisic added: "Not so much.
"He said to keep working and I have to improve myself in training and try to get back in the line-up.
"It is not going to be easy here, but it was never going to be easy."
Pulisic has made six appearances in all competitions, with the American star yet to open his account for Chelsea, who are sixth 11 points adrift of runaway leaders Liverpool.