Artur Boruc - 5.5
Boruc failed to catch the simple balls in his penalty area and spilled the ball even when he was not under pressure. His defenders failed to do their job well and there was nothing much he could do about the goals he conceded.
Maya Yoshida - 6.5
Despite Fonte being the captain, it looked like Yoshida was the boss in defence and had a very promising start to the game - until Chelsea got their equalizer and everything went out the window.
Jose Fonte (64' off) - 4
His tackling was definitely too soft for his manager's liking and it was his poor clearance that eventually led to Chelsea's fourth goal. If he had made a proper clearance earlier on, not only would he have prevented Ba from scoring a second but he could have prevented himself from picking up an unnecessary injury while sliding in on Ba.
Luke Shaw - 7
There is still plenty of room for improvement for young Shaw, who fared well against Hazard and Azpilicueta. Fortunately for him, he had the pace to cover up any defensive holes whenever there was a slip in the back four.
Morgan Schneiderlin (55' off) - 6
He diligently tracked the late runners from midfield and was the link between defence and attack whenever his side has possession, but had to be sacrificed as his side were looking to take the game to Stamford Bridge.
Steven Davis - 6.5
His experience at Aston Villa and Fulham proved to be crucial in this tie and was always there to clean up the mess. His weak attempt to clear the ball however, led to Ba scoring the equalizer which proved to be the turning point in the match.
James Ward-Prowse - 7
After watching his performances on the field, one can easily forget that he is only at a tender age of 18. Confident with the ball, he bossed the midfield for the Saints but failed to conjure a comeback for his side in the second half.
Jack Cork - 7
The former Chelsea player remembered whatever his former employers taught him in defence and used it against them. A solid all round display from him.
Guilherme Do Prado - 5.5
His 100th appearance for the Saints was a relatively subdued one, lacking in penetration and seemingly void of confidence. It was his killer pass that set up Rodriguez for the opener to help his side earn a surprise early lead.
Jason Puncheon (78' off) - 5
Unlike the Arsenal game where he terrorized Kieran Gibbs, he could not work his magic against the experienced Cole and with both the wing players from Southampton struggling to get involved in the game, it was a matter of time before Chelsea ran riot and that they did.
Jay Rodriguez - 6.5
The highlight of his game was that sublime finish past Turnbull to shock the men in blue. He did absolutely nothing after that and was no match for Ivanovic and Cahill.
Steve De Ridder (55' on) - 6
Forced Turnbull to make his first real save of the game. With the entire goal to aim at, he fired straight at the Chelsea keeper.
Jos Hooiveld (64' on) - 6
The big centre-back came on in place of the injured Fonte but there was little he could do as his team was already trailing 4-1 by the time he arrived on the pitch.
Lee Tadanari (78' on)
Ross Turnbull - 7
Turnbull showed why he is an able replacement for Petr Cech in this game. He was not involved for the majority of the game until he was called upon to pull off that double save which could have otherwise got Southampton back in the game.
Branislav Ivanovic (65' off) - 7.5
Ivanovic took his goal tally to 6 this season with an excellent strike from open play - a surprise as most of his goals have come from set pieces. A trustworthy defender who keeps his concentration for the full 90 minutes.
Ashley Cole - 7
Cole was uncharacteristically shaky in the opening minutes but eventually recovered and order was restored, running freely up and down the flanks.
Gary Cahill - 6
Cahill was nowhere to be seen when Rodriguez crept in behind the back four to stun the Blues but was dominant in the air nonetheless, heading away any ball aimed at Southampton's lone striker.
Cesar Azpilicueta - 6
The rampaging full back had an easy time defending against Do Prado, but his positioning would come into question when Rodriguez ran straight into the penalty box unchallenged. His crosses from the right were poor as well, over-hitting them most of the time.
Ramires - 7
Ramires was his usual self, making those tireless runs all around the pitch and ensured Chelsea always had an outlet on the counter.
David Luiz - 5.5
Luiz is clearly loving his midfield role in the team but was guilty for giving away possession on countless occasions. He was switched back to defence late in the game, and that was when Chelsea looked a lot better.
Juan Mata (79' off) - 9
The Spaniard had a big part to play in the equalizing goal, wriggling his way around in tight situations before presenting it on a platter for Ba to tap the ball into an empty net. It was an excellent overall performance from Mata, who pulled the strings for his side an always sent dangerous passes through to set up the attack.
Eden Hazard - 6.5
Hazard had a few brief moments of brilliance, but did not trouble the Southampton defence as much as his manager would have hoped. Nobody would highlight his under par performance anyway as the rest of his team mates sparkled.
Victor Moses (73' off) - 7
He gave the visitors the lead with an instinctive left footed finish across goal, leaving Boruc no chance seconds before the half-time whistle. After the arrival of Benitez, Moses finally got more time on the pitch and is slowly rewarding his manager's faith in him.
Demba Ba - 8
His first start in a blue shirt turned out to be one to remember for Ba, who was only a goal shy from claiming his hat-trick on his debut. Extremely effective at both ends of the pitch, Ba was defending from corners and causing the opposition all sorts of problems with his brute strength while grabbing two goals with some excellent predatory finish.
Frank Lampard (65' on) - 6.5
The loyal servant's 193rd goal for Chelsea came from the spot after flicking the ball on to Davis' hand, who unfortunately was inside the penalty box.
Marko Marin (73' on) - 6
Marin did not do himself any justice with his performance against QPR and came on merely to get more playing time. Everyone knows what he is capable of after watching him play at Werder Bremen and he just needs more time before Rafa Benitez will have a selection headache.
Oscar (79' on)