On 13 June Chelsea and Bayer 04 Leverkusen reached an agreement for the transfer of André Schürrle, subject to the completion of legal documentation and related matters, including personal terms and passing a medical.
On 21 June, the club announced a contract extension with Adidas that will see them supply the club kits until 2023. This deal means that Chelsea, along with Arsenal, hold the record for the biggest shirt deal in the history of the Barclays Premier League, valued at £300 million.
Chelsea completed the signing of André Schürrle for a fee of around £18.75 million. Schürrle became Mourinho's first signing since returning to the club, signing a five-year deal. He is the first player to wear the number 14 shirt since Claudio Pizarro in 2007–08.
On 1 August, Chelsea announced that senior reserve goalkeeper Henrique Hilário had signed a new one year deal after his contract had expired in June. Another youngster was signed, teenage Croatian striker Stipe Perica. 18 year old defender Nathan Aké signed a new five-year contract with Chelsea, he made six appearances for the Blues last season.
On 30 August Chelsea were beaten in the UEFA Super Cup by Bayern Munich on penalties at the Eden Arena in Prague. The match was a tense encounter, dominated by Bayern but Chelsea were dangerous on the break, they opened the scoring through a fantastic strike from Fernando Torres, who was set up by Andre Schurrle who had received the ball from Eden Hazard following a mazy run. Bayern equalised through a sweetly struck shot by Franck Ribery inside Petr Cech's near post. With 5 minutes left Ramires was sent off for a second bookable offence leaving Chelsea to face extra-time with 10 men. Early in the first half of extra-time Hazard put Chelsea ahead after beating two Bayern defenders and wrong-footing Manuel Neuer. Chelsea managed to hold on until the final 5 seconds after spending much of extra-time camped in their own 18-yard box, but Javi Martinez broke their hearts putting the ball past Cech after a deflection carried it into his path. During the penalty shoot-out, all the players on both sides scored their penalties up until Chelsea's final penalty taker Romelu Lukaku, hit a tame penalty that was saved by Neuer, thus sealing the win for Bayern.
On 14 September, Mourinho suffered the first defeat of his "second coming" as Chelsea were defeated 1-0 by Everton through a Steven Naismith header in first-half stoppage time, after an impressive defensive display by the Merseyside club at Goodison Park. 4 days later, Chelsea suffered a shock defeat by Basel in their opening group game in the Champions League at Stamford Bridge. Chelsea opened the scoring just before the interval through a tidy finish by Oscar from 8 yards out, however two quickfire goals for Basel in the last 15 minutes from Mohamed Salah and Marco Streller condemned Chelsea to their first ever loss in an opening group game of the Champions League.
Chelsea won their following fixture in the Premier League on 21 September after a four game winless streak and two game losing streak in all competitions against Fulham. The two-nil victory was secured by two close-range finishes by Oscar and John Obi Mikel respectively, the latter being a staggering surprise as Mikel had not scored for Chelsea since 2007 and became the source of many jokes between Chelsea fans.
On 1 October, Chelsea convincingly defeated Steaua București in Romania by 4 goals to nil in their second Champions League group game. The rout was started with a tap-in from Ramires, followed by a saved Samuel Eto'o shot rebounding off a defender's shin for a second. In the second half, Ramires completed a brace with a strong shot into the near post after impressive wing-play by Andre Schurrle and Frank Lampard finished Steaua off with a trade-mark goal, a low shot from 18 yards skimming in off the base of the far post. Chelsea won their third game in a row by defeating Norwich 3-1 at Carrow Road on 6 October. Chelsea went ahead in the 4th minute through an 18-yard strike from Oscar, however they were pulled back in the 68th minute by an Anthony Pilkington header before Eden Hazard scored the winner from a quick counter-attack, the win was sealed with a spectacular finish from Willian, scoring his first for Chelsea.
Chelsea continued their fine form, beating Cardiff City 4-1 on 19 October - their 3rd consecutive win in all competitions. Cardiff opened the scoring through Jordon Mutch, capitalising on a David Luiz mistake, however Chelsea dominated the game from there on in, with two goals from Eden Hazard, and high quality finishes from Samuel Eto'o and Oscar that completed the rout. This victory preserved Chelsea's 100% home league record. Three days later, Chelsea earned three valuable points after defeating Schalke 04 3-0 in their third Champions League group game, with Fernando Torres getting a brace and Eden Hazard scoring late on through an impressive solo effort.
On 27 October Chelsea faced Manchester City, a highly important game for both sides looking to continue strong league forms. The match was a tense encounter in which Fernando Torres played superbly, netting a late winner following a defensive mix-up after setting up Andre Schurrle for Chelsea's first. Manchester City equalised through Sergio Aguero early in the second half, however they could not hold on for a point.
Chelsea completed the signing of promising 18-year-old midfielder Bertrand Traoré on a four-and-a-half-year contract. He had previously played for the Blues on the pre-season tour of Asia and scored against the Malaysia Xi and the Indonesia All Stars.
An underwhelming Chelsea display ended in defeat by Newcastle on 2 November, with goals from Yoan Gouffran and Loic Remy. In a post-match interview, Mourinho expressed his bewilderment at the result, "I am angry, because I don't understand why after a fantastic run of matches, we lose this game"(BBC MOTD). Chelsea continued their strong Champions League form by defeating Schalke 04 3-0 at Stamford Bridge on 6 November in their fourth group game with a brace from Samuel Eto'o and an acrobatic volley from Demba Ba, thus making it three consecutive wins without conceding a goal.
Three days later, Chelsea drew 2-2 with West Brom at home, a last minute Eden Hazard penalty saving the point. On the 23 November, Chelsea returned to winning ways following the international break with a 3-0 win against West Ham at Upton Park. A brace from Frank Lampard either side of a fine finish from Oscar sealed the win for the Blues and moved them up above Southampton to third. Chelsea again displayed inconsistent form by losing 1-0 to Basel on 26 November, without registering a shot on target.
Chelsea started December with a home win against Southampton, continuing their strong home form in the league. The Saints took a shock early lead, Jay Rodriguez finding the back of the net with only 13 seconds on the clock. The Blues came back to win through second half goals goals from Terry, Cahill and a late goal from substitute Demba Ba. Chelsea's next match saw them defeat a spirited Sunderland side 4-3 in a thrilling, topsy-turvy encounter at the Stadium of Light; yet again the Blues went behind but were able to fight back to get the win following a mercurial display by Eden Hazard, who scored a brace. After three wins on the trot Chelsea went to the Britannia Stadium looking to close the gap on leaders Arsenal to 1 point. Having gone 1-0 up through a solo effort from Andre Schurrle things seemed to be going well, but Stoke capitalised on a defensive error to go into the break 1-1. A Stephen Ireland goal put the hosts ahead, but not for long as Schurrle scored his 3rd of the season and 2nd of the match, again from outside the area. A draw was looking likely when Liverpool loanee Oussama Assaidi gave Stoke the 3 points with a curling strike from 20 yards to send Mourinho's men away empty-handed.
Chelsea travelled to the Stadium of Light for the second time in a month to face Sunderland in the quarter-final of the League Cup. Despite leading for most of the second half through a scrambled Frank Lampard finish (this goal was the first incident to require the use of hawk-eye technology in League Cup history) and barely being troubled by their opponents' attack, a late equaliser from former Chelsea man Fabio Borini pushed the game into extra time, where a 118th minute winner from Ki Sung-Yueng saw Chelsea dumped out of the Capital One Cup. On 23 December, Chelsea faced a tough trip to Arsenal yet they came through it unscathed drawing 0-0.Petr Cech and the Chelsea defence kept their first clean sheet since the 3-0 victory over West Ham. On Boxing Day an Eden Hazard goal granted Jose Mourinho's team a 1-0 win over Swansea. Chelsea's final game of 2013 ended in a superb victory over Liverpool. Despite going behind after 3 minutes, goals from Eden Hazard and Samuel Eto'o moved the Blues 4 points ahead of Liverpool and 2 points behind leaders Arsenal.
Chelsea kicked off 2014 with an impressively comfortable 3-0 away victory against this season's surprise package Southampton. Southampton kept Chelsea at bay until midway through the second half when Mourinho made a double substitution, taking Schurrle and Mata off for Willian and Oscar, whose deflected cross was tapped by Torres in the 60th minute, and later scored himself in the 82nd minute following a good strike by Willian.
Unbeknownst to all this would be Juan Mata's final Chelsea appearance, reacting angrily to his substitution in the 53rd minute following a mostly poor season, spending most of it on the bench. Over the course of 2 and a half seasons, Mata made 135 appearances for Chelsea, scoring 33 goals and winning both the Champions League and the Europa League alongside the FA Cup following a highly successful spell at the club, winning the Chelsea player of the year award two seasons consecutively.
Chelsea began their 2014 FA Cup campaign with a comfortable 2-0 win against second tier side Derby County, managed by former England coach Steve McClaren. Victory came courtesy of a rare John Obi Mikel goal, scoring his second of the season despite not having scored since 2007 before his goal against Fulham in October, followed by an Oscar goal 20 minutes from time that sealed the win. On 11 January, Chelsea won their 4th consecutive league game at the KC Stadium with a 2-0 win over Hull City with goals from Hazard and Torres.
Chelsea made it 5 league wins on the trot with an impressive 3-1 home win against Manchester United on the 19th, a Samuel Eto'o hat-trick winning the day. Chelsea progressed to the Fifth Round of the FA Cup with a 1-0 victory over Stoke City, the winner being a superb Oscar free kick in the first half. However Chelsea failed to complete a perfect January as they drew 0-0 to relegation candidates West Ham United. Chelsea had 39 shots throughout the game and failed to score. This was the first time since the 2003-04 Premier League season that this has happened.
Chelsea's 14 Premier League unbeaten run came to an end at Aston Villa in controversial fashion. Willian was sent off after two debatable yellow cards, before Fabian Delph scored a superb winner for the Villains. However Ramires was sent off for a poor foul on Karim El Ahmadi and Mourinho was subsequently sent to the stands for protesting Ramires red card. Despite the loss Chelsea still remain 4 points ahead of nearest rivals Liverpool.
Chelsea finished March in disappointment as they succumbed to defeat at Selhurst Park. John Terry scored an unfortunate own goal after 52 minutes as Chelsea lost top spot for the first time since the beginning of February.
Despite a disappointing campaign for the first team, the Chelsea Youth team won the 2013–14 FA Youth Cup. A late Dominic Solanke brace helped the young Blues come from 3-2 down to defeat Fulham 7-6 on aggregate and secure their third title in five years.
The home kit featured very subtle blue pinstripes on the shirt and the socks featured more blue. The away kit was a simple reverse of the home kit, aside from the red trimmings. The third kit was just a pure all-black, and it didn't contain any spectacular details this season, in contrast to recent years. The new goalkeeper kit was launched, and it turned out to be mainly yellow with black sleeves. The dark green goalkeeper outfit and the white/maroon goalkeeper outfit (from 2012 and 2011, respectively) were retained and worn in few matches.