The Reds had chances to take the lead but gifted their hosts several goals with sloppy individual errors. It was their joint heaviest defeat in a cup game since an 8-1 loss against Derby County at The Baseball Ground in the FA Cup in 1897.

Gerhard Struber made five changes from the side that lost 2-0 at Reading four days earlier. Brad Collins, Aapo Halme, Callum Styles, Cauley Woodrow and Patrick Schmidt replaced Jack Walton, Conor Chaplin, Luke Thomas and the suspended duo of Michal Helik and Mads Andersen. Clark Oduor and Elliot Simoes made the bench after injury alongside teenage centre-back Jasper Moon.

Chelsea should have taken the lead within the first minute when their £70million signing Kai Havertz played in England international Callum Hudson-Odoi on the right of the box but former Chelsea goalkeeper Brad Collins made a fine one-on-one save.

Barnsley began to grow into the game and Styles had a shot blocked in the home box after meeting a cross by Kilian Ludewig. Woodrow's 25-yard strike was tipped over by goalkeeper Willy Caballero then, after the resulting corner was cleared, Halme headed a Ludewig cross into the goalkeeper's arms from close range.

Collins then made another save from Havertz's weak shot on the left of the box after Alex Mowatt lost the ball and Mason Mount found the German. The opening goal came on 18 minutes when Ritzmaier passed the ball back to Halme who was robbed of it by England striker Tammy Abraham who beat Collins in a one-on-one situation.

Ritzmaier forced another save from a tight angle on the left of the box then Mount hit the side netting from a tight angle.

The second goal saw Abraham brilliantly dummy a pass by Mount in the box and the ball ran to Havertz to fire in from eight yards out.

Caballero made another save, turning a 20-yard Schmidt effort around his right corner then Michael Sollbauer headed wide from close range at the back post from Ritzmaier's corner.

Struber brought Thomas on for Woodrow at half-time. It was 3-0 four minutes after the interval when captain Mowatt was tackled just outside his box by Havertz and Ross Barkley ran through to score.

The fourth goal saw Sollbauer robbed by Mateo Kovacic on the left wing then his low cross was brilliantly backheeled by Abraham into the path of Havertz who fired in from ten yards out. The hat-trick was completed when Collins ran out of his box to try to clear an excellent pass by Abraham but was beaten to it by Havertz who rounded him then tapped into the empty net.

Schmidt shot straight at the goalkeeper from 20 yards out then Barkley missed an open goal after substitute Oliver Giroud squared to him. Substitute Clarke Oduor then forced another routine save out of Caballero with a shot from just inside the box. Cesar Azpilicueta headed a good chance wide at the back post from a Kovacic cross.

The sixth goal came from a stopping header by Giroud who met a left-wing cross by Ben Chilwell.

Barnsley (3-4-1-2): Collins; Sollbauer, Halme, J Williams; Ludewig, Mowatt, Ritzmaier (Oduor 57mins), Styles; Woodrow (Thomas HT); Frieser (Chaplin 57), Schmidt.Subs: Walton, Moon, Simoes, Adeboyejo Yellow cards: Collins.

Chelsea (4-3-3): Caballero; Azpilicueta, Tomori, Silva (Zouma 61mins), Emerson; Barkley, Kovacic, Mount; Havertz (Chilwell 67); Abraham (Grioud 72), Hudson-Odoi. Subs: Baxter, James, Jorginho, Werner, Giroud. Goals: Abraham 18; Havertz 28, 54, 65; Barkley 49; Giroud 83.