Much was expected of Werner after Chelsea saw off competition from Premier League champions Liverpool to sign the Germany striker from RB Leipzig.
The 24-year-old scored seven goals in seven games for the Blues earlier in the season but has now gone 12 matches without hitting the back of the net.
Werner failed to end his goal drought in Sunday’s 3-1 defeat to Man City and even managed to hurt himself while attempting to take a corner during the Premier League fixture.
The £50m striker tried to take a quick corner as Chelsea chased late goals but kicked the corner flag before the ball and dropped to the floor. Werner appeared in discomfort and limped away from the corner flag.
Chelsea were outplayed by Manchester City on Sunday and goals from Ilkay Gundogan, Phil Foden and Kevin de Bruyne saw Pep Guardiola’s side clinch a routine win.
The Blues have now won just one of their last seven matches in all competitions, with pressure mounting on manager Frank Lampard.
Speaking after the 3-1 defeat, Lampard said: ‘Mistakes, individual mistakes, not getting close enough. They punished us.
‘I am not trying to talk up the last 20 minutes of the game because at 3-0 the vitals of the game have changed but I was still looking for a reaction.
‘I am not putting ourselves down. I am the man to have the reality check and there will be work and at times pain.
‘Today was painful in the first half in football terms because their level of play show where we need to aspire to. In the second half I saw a reaction but the work needs to be done.’