So which one is the real Timo Werner?
Or is it the one who fired wide with the goal gaping that left his manager open-mouthed in shock?
Thomas Tuchel will certainly hope it is the former. And after seeing Werner score for the first time in 12 games, he will hope this sparks a turnaround in form for the £45million striker.
But on a day when he showed the best and worst of his qualities, it is just too hard to tell what this means for the German.
Crucially for Tuchel, he came up with the decisive moment at the London Stadium to move Chelsea three points clear of West Ham in fourth and four ahead of Champions League rivals Liverpool.
One goal was enough to separate the sides – and given Tuchel’s effect on a Chelsea defence that kept a 17th clean sheet in 21 games under his rule, more often than not, one is all it takes.
But going forward, if they are to prove themselves genuine title contenders next season, they will have to find their cutting edge.
The question is whether Werner will be able to provide it.
Had he converted his second-half chance when racing in to clean up after Mason Mount’s long-range effort had been palmed away by Lukasz Fabianski, the game would never have been in doubt.
Instead, his glaring miss meant Chelsea were susceptible to a West Ham comeback – and would perhaps have been more vulnerable if not for Fabian Balbuena’s controversial red card.
Tuchel knows the area of his team most in need of address. He will also know how close he is to a side that can compete with Manchester City over the course of a season - and possibly a resurgent Liverpool - next term.
Defensively Chelsea are watertight.
In midfield he has energy and options in N’Golo Kante, Jorginho and Mateo Kovacic – even if he could do with more creativity.
It is up front where his side fall short.
They can be too predictable, too easy to snuff out – as Brighton managed on Tuesday.
They do not create enough clear-cut openings – and when they do, they are not decisive enough in front of goal.
The good news is, such issues can be resolved with a signing or two.
Erling Haaland takes this Chelsea team to the next level.
Even an aging Sergio Aguero provides a ruthlessness they simply do not possess right now.
Can Werner provide it long term? The jury is still out as he approaches the end of his first season in English football.
The fact this is a debut campaign in a new country is justifiable mitigation.
He has been involved in 23 goals this season – scoring 11 himself and providing 12 assists.
With such statistics, he can hardly be considered a passenger – and it is easy to see why Tuchel has stuck with him despite his wretched scoring form.
The Chelsea manager has offered him public and private support – yet still believes the club need to invest in a prolific striker in the summer as he targets a Premier League title bid.
Perhaps it is a case of recasting Werner – not as a leading of the line, but a wide forward who does not carry the burden of being the main goal threat.
Perhaps he would thrive playing off a Haaland or Aguero as Chelsea’s equivalent to Mo Salah or Sadio Mane.
Or perhaps he just needs to get through this first season, which could still see him walk away with a Champions League winners’ medal and the FA Cup.
It is hardly shaping up to be a disastrous debut year at Stamford Bridge – just not the explosion of goals Chelsea expected from a player they had to beat Liverpool and Real Madrid to the signature of last summer.
If his winner does prove to help him rediscover his scoring touch, he could yet have a major say on Chelsea’s campaign.
In turning home Ben Chilwell’s 43rd-minute cutback, he succeeded in putting Chelsea in control of their own destiny - and perhaps provided a glimpse of his own promising future in blue.