Arsene Wenger's pre-match warning turned out to be an ominous one.
He had warned his players of the scheming Diego Costa.
His words, however, fell on deaf ears.
Instead, Arsenal's mission to make a strong statement of intent at the Emirates Stadium came to a disastrous conclusion, wrecked by Chelsea's specialist of the dark arts.
Once more, the much-loathed Costa got under their skins, as Chelsea carved out a 1-0 win over the Premiership title hopefuls this morning (Singapore time).
The controversy arrived early.
In the 18th minute, Costa swung the balance in Chelsea's favour, when he crashed to the turf under the challenge of Per Mertesacker as he beat the offside trap.
The Arsenal centre back received his marching orders, as a screaming Costa writhed in pain.
Where his discomfort came from, no one could really tell.
The television replays will put referee Mark Clattenburg in the spotlight for the next couple of days, as there didn't seem to be any contact between the two players. Even if there was, it would be miniscule.
Mertesacker cannot escape culpability though, for his decision to attempt a tackle so risky that early in the match.
The home team did not even have much time to digest the sense of injustice when Costa twisted the knife in their wound five minutes later.
A superb cross by Branislav Ivanovic was all the invitation he needed to thump in a venomous shot from close range.
The destruction was complete.
The mind raced back to the reverse fixture at Stamford Bridge last September, when the Blues emerged 2-0 victors.
Defender Gabriel Paulista was the one goaded into kicking out at him then, earning a red card just before half-time.
Arsenal ended that match with only nine men, after Santi Cazorla also got sent off, 11 minutes from time.
There was clearly a lesson to be learnt there, one which Wenger identified and one which his charges failed to heed.
Costa's goal this morning turned out to be the game's only one.
But it was enough to land a potentially debilitating blow to the title hopes of the Gunners, who needed the three points to return to the top of the English Premier League table, above Leicester City on goal difference.
To Arsenal's credit, they fought hard and pulled out all the stops.
Wenger replaced striker Olivier Giroud with Paulista to make up for the loss of Mertesacker immediately after the sending-off, and introduced in the 57th minute Alexis Sanchez, who had just recovered from injury,
The players responded in the best way possible under the circumstances, fighting till the final whistle.
In fact, they had a handful of good chances.
Mathieu Flamini had arguably his team's best opportunity to equalise on the stroke of half-time, but hooked his shot over the bar from close range.
Close to the hour mark, a goalmouth melee in the Chelsea penalty box ended with a block by a Chelsea defender on Paulista's toe-poke.
In the closing stages, the Gunners poured forward in an attempt to rescue a point.
But it was in vain.
The game was already lost much earlier, the moment they gave Costa the chance to rub salt in their wound.
This article was first published on January 25, 2016.
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