The Leipzig iteration was a flying centre-forward who drifted out to the left before cutting inside, often on the counter-attack, to devastating effect.
The Chelsea version appears low on confidence, and a shadow of his former self.
On the face of things, four goals and three assists in 12 games during your maiden Premier League campaign isn’t grim reading at all, but a few Werner's misses could be fairly categorised as glaring, and his all-round performances haven't inspired.
The German's display in Tuesday night’s 2-1 defeat to Wolves summed up his recent form; zero shots on target, several lacklustre dribbles and countless slack passes accounted for a poor showing overall.
It has become increasingly apparent that Werner is a centre-forward, not a winger, but injuries have meant that he’s rarely played through the middle, and that has clearly affected him.
Julian Nagelsmann is renowned for getting the most out of his forwards - struggling Newcastle striker Joelinton managed 18 goal contributions under his guidance in 2018/19 - and Leipzig’s system was built entirely to create Werner plenty of chances.
But, while it’s too soon to say that the forward's move to Stamford Bridge won’t work out, it could be time to take him out of the limelight for a while.
So, if that happens, who could replace him?
The 27-year-old has not yet hit full fitness or top form at Stamford Bridge, but already seems crucial in Frank Lampard’s system.
With one goal and three assists in five Premier League starts, along with an xA per 90 of 0.62 (a tally that nobody with over 200 league minutes can match) Ziyech has taken to English football like a duck to water.
He has been sorely missed in recent games, with Chelsea struggling in the absence of his creative flair.
Onto Callum Hudson-Odoi.
The Englishmen seems to be touted for a move away from West London every transfer window, yet he’s remained at the club despite a lack of first-team minutes.
This year is no different.
However, with Werner out of form, and both Ziyech and Christian Pulisic injury prone, he could get his chance in the coming weeks.
When the American has played this season he has done well. In fact, in all competitions, he has already matched his goal tally from the entirety of 2019/20 (three), and looks ready to make the step up to regular first-team action.
Both Ziyech and Hudson-Odoi are set to return to training this week, and are likely to be fit for the clash with London rivals Arsenal on Boxing Day; could they take the place of their struggling teammate Werner?
The Youngster: Faustino Anjorin
The teenager made his first-team debut for the Blues against Grimsby in the Carabao Cup in September 2019, before making his Premier League debut six months later in a 4-0 victory over Everton.
Having already won the group, Lampard handed Anjorin his Champions League bow against Krasnodar earlier this month and there have been calls for him to be included in the Premier League squad in the next few weeks.
Capable of playing as a no.8 or a left winger, his future will most likely lie in central midfield, but he performed admirably out wide against Krasnodar and could fill in there to give Werner a rest.
The Outside Shout: Valentino Livramento
Remember the name Valentino Livramento - now this would be a wildcard.
Chelsea seem to have a habit of producing outstanding young, attacking right-backs and they’ve done it again.
Reece James, Tariq Lamptey and now Livramento.
Unlike his predecessors, however, Livramento is more than adept at playing as a right winger, something he done frequently this season while producing two goals and seven assists in 13 games.
It’s most likely too early for Livramento to make a dent into the first-team set-up, but his introduction out on the right would allow Pulisic to play his preferred position on the left wing while still giving Werner a break.
With no perfect option available, Lampard may well have little choice but to keep faith Werner for now.
However, if the manager does decide to rest his struggling forward against West Ham, then it will most likely be Anjorin who takes his place.