He had publicly indicated his preference to move to Premier League leaders Liverpool but they were unwilling to pay the release clause in the current climate.
Chelsea failed with a bid to sign Mertens in the last transfer window and the Belgian is now expected to pen a new contract with Napoli.
Wolves and Sheffield United are five points adrift of Chelsea, the latter with a game in hand, while Tottenham can not be discounted due to Harry Kane's return, despite a seven-point gap.
The Germany global striker has a €55m (£49.4m) release clause which expires on Monday June 15.
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Colin Kaepernick kneeling during the national anthem comes up a lot as the evidence. "I imposed a curfew at 7pm", she tweeted . Three other officers involved in the incident have been fired but not charged. "Act fast!" Mr Trump tweeted on Tuesday.
Advancing talks for Werner come after he instructed clubs of his disinterest in moving in January with the Blues having targeted a forward during the winter window.
It remains to be seen if the goal machine would be keen to swap RB Leipzig for the London giants.
But given Lampard's ambitions of restoring Chelsea as a major challenger in domestic and European competitions, the addition of Werner - added to that of Ziyech - certainly boosts their chances of doing so, while also ensuring Liverpool do not strengthen further.
Speaking earlier this week about the possibility of losing the striker, Leipzig boss Julian Nagelsmann said, "He knows what he has in Leipzig and also what he has with me".
"In the end, it is his life, his career, he can decide that".