The Blues lost 1-0 away at Middlesbrough in the first leg of the semi-final.
And it means the pressure is on to win in the reverse match at Stamford Bridge on January 23.
Plus there will be another 90 minutes for a host of first-choice players in an already-hectic schedule.
Hayden Hackney lost Moises Caicedo in the area as Boro got in behind the Chelsea defence on 37 minutes.
His smart finish from close range sparked wild scenes at the Riverside as fans started dreaming of a trip to Wembley next month.
Middlesbrough could have been ahead earlier after Axel Disasi slid in on Emmanuel Latte Lath with just 40 seconds on the clock – but escaped with no VAR in use.
But at the other end, Cole Palmer will be ruing THREE big misses before the break – dragging one wide, putting a simple rebound over then hitting Tom Glover with another.
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