Kepa Arrizabalaga
The goalkeeper's first appearance under Thomas Tuchel and he made a vital stop in the first half to deny Callum Brittain. Also showed bravery to come out and collect a corner with the Blues under pressure during the opening 45 minutes.
He was more of a bystander in the second period but did flap at a ball into the box late on which almost enabled the home side to score. Did well late on as Barnsley threw crosses into the box. 7
Andreas Christensen
Given his impressive displays against Tottenham and Sheffield United in the middle of the defence, it was a curious decision by Tuchel to use Christensen on the right of the back three.
The Dane was busy throughout the first half, but made several important interceptions to half Barnsley attacks.
He took a blow to the head late in the final minutes of the opening period and didn't reappear at the break. Hopefully, it was a change made as a precaution. 6
Kurt Zouma
The Frenchman started in the middle of the back three and appeared uncomfortable in the role. His distribution was poor in the first half, with several passes forward not finding a target.
The half-time change to a back four helped Zouma settle into the game. There was less pressure on him to build attacks and he was able to help keep Barnsley at bay alongside Antonio Rudiger. 6
Emerson
Emerson started on the left side of the back three in his first outing under Tuchel and the Italy international struggled in the opening half as Barnsley overloaded his flank.
Was moved to his favoured left-back role after the half time interval and was far more assured. It wasn't a display that will get him in the Premier League side. 6
Callum Hudson-Odoi
The 20-year-old returned to the right wing-back role he impressed in during Tuchel's first two matches in charge.
There was some nice touches from Hudson-Odoi in the opening period but he was forced to do plenty of defending and was caught upfield more than once.
Played as a left winger in the second half and flashed a shot across goal as Chelsea searched for an opener. His influenced waned as the match progressed. 6
Billy Gilmour
This was the 19-year-old's first appearance under Tuchel and he started in a midfield two alongside N'Golo Kante. For much of the first half, however, Gilmour was unable to have his usual influence on the game.
Barnsley restricted passing avenues into the Scotland Under-21 international and any time he did receive the ball, he was forced to go back..
He improved after the break playing in a midfield three. Gilmour was able to drop deeper to collect possession from the centre-backs and knitted attacking moves together in his customary style.
He also played a key role in Chelsea's goal; it was Gilmour's pass that enabled Reece James space to cross for Tammy Abraham to convert. 7
N'Golo Kante
Kante started at Oakwell as he continues to build his fitness following a month-long absence due to injury. Understandably, he wasn't quite his normal self. He was caught in possession far too often and that led to Chelsea being unable to build from the back.
In the second half, he played as a number six and improved. Played a clever pass in the build-up to Abraham's goal and helped keep Barnsley from grabbing an equaliser. 6
Marcos Alonso
Another start for the Spaniard under Tuchel but Alonso was poor in the first half. He was caught upfield far too often and left Emerson with too much to do when crosses were delivered to the back post. The 30-year-old made no impact in an attacking sense before being brought off at half time. 5
Hakim Ziyech
Ahead of the game, Tuchel said he hoped Ziyech would produce a performance that matched his efforts in training. It didn't happen.
There were a couple of nice first-half touches from the Morocco international but the game largely bypassed him.
Chelsea's formation change at half time saw Ziyech move higher up the pitch yet he still struggled to have an influence. His standout moment was a free-kick that was headed wide by Rudiger. It was a night to forget for the 27-year-old. 5
Christian Pulisic
The American missed the win over Sheffield United for family reasons so was fresh for the trip to Oakwell. He didn't look it, though. Throughout the opening period, Pulisic attempted to break through with the ball only to be halted by a Barnsley defender.
It was the same story in the second half despite Pulisic being moved out to the right flank. We've still not seen the best of the winger this season. 5
Tammy Abraham
Abraham cut a frustrated figure throughout the first half. The Barnsley defence pushed high and cut the 23-year-old out of the game. He admittedly wasn't helped by the lack of supply.
It was a similar story in the second period but Abraham is a goalscorer. He only needs one chance. And he proved that when it arrived.
A slick passing move resulted in James squaring the ball across the box and Abraham was on hand to finish.
The academy graduate held the ball up well for Chelsea during the remainder of the contest and had one more vital moment, heading a Michael Sollbauer shot destined for the net over his own crossbar. 8
Substitutes
Antonio Rudiger (for Christensen, 45)
Introduced at the interval as Chelsea moved to a back four, the German slotted in alongside Zouma and helped Chelsea improve with the ball. Had a header go narrowly wide as Chelsea searched for an opener. 6
Reece James (for Alonso, 45)
Came on to help Chelsea in attack as much as defence and did just that. It was his run forward and cross which enabled Abraham to tap home. 7
Tino Anjorin (for Ziyech, 69)
Given his first game time since the third-round win over Morecambe, Anjorin looked sharp and there were a couple of encouraging runs with the ball. Gave Chelsea more of a physical presence than the man he replaced. 6
Mateo Kovacic (for Pulisic, 80)
Not enough time to have a major impact. N/A
