The warning signs could hardly have been clearer for Barcelona. When Willian picked up the ball 25 yards from goal midway through the second half, there was an air of inevitability that the ball would end up in the net.
Earlier in the game, he had fired his first warning shot, a bullet of a shot from range that took a layer of paint off the right post.
Soon after, he hammered his point home by slamming another effort off the other side from closer range. 'I'm up for this one,' the shot whispered threateningly to the static defence who watched it bounce wide.
And yet, when the ball dropped to him once again in the second half, there wasn't a Catalan shirt in sight. Seconds later, as Marc-André ter Stegen slumped to retrieve a shot he could have had no hope of saving from the bottom corner of his net, Willian had scored his sixth Champions League goal from outside the area in Chelsea colours. Since moving to Stamford Bridge, no player has scored more.
Master of the craft allowed to punish Barca
Why, then, was he allowed to shoot so freely from range, when it is clearly a skill he has mastered?
Is it simply, as Jonathan Wilson has suggested in the Guardian, a case of 'Arjen Robben syndrome'? That the Brazilian shifting the ball onto his right and shooting, like Robben on his other foot, is simply one of those things that simply happens - everybody knows what is going to happen, but nobody has figured out how to stop it?
Or, to pick up on the post-match TV punditry, did Willian actually benefit from his own unresolved reputation? Few would argue that he is a player capable of doing wonderful things on the pitch but, as Steven Gerrard and Frank Lampard noted on BT Sport, he doesn't do it enough.
Hazard draws praise and defenders
To compare, it is hard to imagine that Eden Hazard would have been afforded the same luxury of time on the ball as did Willian, had he been in the same position.
With Alvaro Morata on the bench, the Belgian was the undisputed star of the attack and received the appropriate level of attention from the Barca defenders, partially owing to his central false-nine role.
When he zapped a powerful strike just over the bar from the edge of the area in the opening exchanges, he did so despite a number of players pressuring him and closing him down.
Finding the bottom corner an hour later, he had ample time to test the wind, draw out a diagram of the obstacles in his path, calculate the optimum trajectory for his shot and show his working for full marks.
If the visitors learned their lesson on the third attempt, he won't have the same luxury in the return leg.
Second leg will be tougher
If Willian did indeed benefit from his own reputation as not quite a world-beating talent, his performance on Tuesday night ensured he will be higher up the list of Barcelona's defensive priorities by the time Chelsea visit the Nou Camp.
He won't want there to be an element of surprise every time he takes a game by the horns and bends it to his will - Lionel Messi notwithstanding - but it would be something of a shock if he replicates his stellar performance on Spanish soil.
That has to change if he wants to be remembered as a great player rather than a very good one, but for the time being he can try to reap the rewards of not quite being Chelsea's main man.
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