#3 Patchy pitch contributes to snooze fest
Most of mainstream Europe has been ravaged by extreme winter in recent weeks, and this might have contributed to Chelsea's poor performance.
The state of Barnsley's pitch was nothing to write home about, with large swathes of grass missing on several portions of the field.
This severely affected the state of play, considering that the Chelsea players are more used to playing on lush green fields.
They were largely lacklustre in their passing sequences and lacked the normal fluidity associated with top-flight sides.
The hosts, by contrast, seemed more comfortable on home turf. Although the Blues ultimately got the job done, the state of the field did them no favours.
#2 Even in victory, Chelsea still have questions to answer
Although Chelsea might have gotten the job done, it was hardly a memorable performance from the Premier League side.
A case can be made that most of the players have not had ample time to play under Thomas Tuchel. Meanwhile, the state of the field also contributed to a haphazard performance.
However, that does not excuse the lack of cohesion and precision shown by the visitors.
Questions must be asked of why Chelsea did not force former academy starlet Bradley Collins into a save. Tammy Abraham's goal represented their only shot on target across the 90 minutes.
Tuchel started the game with his now-familiar wing-back system. A lacklustre first half saw him effect changes, with Marcos Alonso going off for Reece James. This prompted a shift to a flat back four, although there was no requisite change in tempo from the visitors.
The brightest spark of the second half resulted in the sole goal for Chelsea, but games like this against lower opposition should not have fans sitting on the edge of their seats.
A more composed side would have punished the Blues with the chances Barnsley created.
It is still early days in the Tuchel era, but criticisms have risen over his side's lack of cutting edge. Chelsea's tame display against Barnsley did little to quell those voices.
#1 Tammy Abraham steps up to spare Chelsea's blushes
Tammy Abraham has consistently delivered the goods in front of goal for Chelsea, but the jury remains out on whether he is the right man to lead the line.
Having ended the Lampard era with a hat-trick in the victory over Luton Town, Tammy Abraham came to the fore once more to secure Chelsea's place in the last eight.
He was well-placed to finish off an excellent pass by Reece James to break the deadlock.
The 23-year-old also showed his usefulness in his own box by clearing a goal-bound shot off the line, with Kepa well and truly beaten.
The battle to be Chelsea's starting striker under Tuchel is an intense one, but Abraham did his chances a world of good with his rounded display against Barnsley.