Substitute Olivier Giroud scored in added time to secure Chelsea's qualification for the Champions League knockout stages with a 2-1 win over Rennes.
Callum Hudson-Odoi's first half breakaway goal seemed destined to be enough for an underwhelming Chelsea side but they were pegged back late in the second period when Serhou Guirassy rose highest to meet a corner and thump a powerful header into the net.
It would be Giroud, cast to the fringes of the Chelsea squad since the arrival of Timo Werner, who would decide the contest as he rose highest to flick home the rebound from Timo Werner's shot and earn Frank Lampard's side their sixth straight win in all competitions. Coupled with a late goal for Sevilla in Krasnodar, Chelsea's win means they will battle it out with the Spanish side for top spot in the group in Spain next week.
Read the key talking points from the game below:
Rennes wasted first half costs them dearly
Though Timo Werner and Mason Mount might have won the game in the first few minutes, Chelsea were certainly not at their best for most of the first half at Roazhon Park even if they ended the period with a one goal lead. Mateo Kovacic was being outshone by Edouard Camavinga whilst Jorginho's passing radar seemed to be malfunctioning as he completed just 82.5 percent of his attempts.
Meanwhile Rennes showed an intensity that they could not achieve with 10 men last time these two met, young wingers Jeremy Doku and James Lea Siliki were constantly forcing mistakes out of their opposing full-backs. And yet what did they have to show for their best moments? Just two shots on Edouard Mendy's goal and a host of wasted opportunities.
Rather than get the ball into dangerous areas Rennes were all too willing to shoot from range or difficult angles, all the more bizarre when Guirassy was such a dominant presence in the air. In total their expected goals (xG) tally of their seven shots was 0.37, i.e. the total quality of the chances they produced in the first half was still some way short of being likely to produce a goal.
That perhaps is the difference between a side like Rennes and the best in Europe, who are able to make very good chances for themselves. Mount's close-range volley that was brilliantly blocked by Alfred Gomis had an xG of 0.56, Werner's close range miss was 0.38xG and Hudson-Odoi's goal 0.41xG.
It seemed like Rennes learned their lesson in the second half, when they found the avenue that worked for them: set-pieces. Barring Thiago Silva and substitute Giroud, Chelsea had few counters to their giant hosts, particularly the tandem of Gerzinio Nyamsi and Guirassy. The simple reality is there was very little the Blues could do against the right delivery and after Edouard Mendy saved well from the former he could not deny the latter, whose brilliant 85th minute header seemed to revive their hopes of victory.
It was a cruel twist of fate that having discovered their aerial superiority they were undone when Giroud rose highest to meet the rebound from Timo Werner's shot and head an excellent looping header into the one spot where no Rennes player could reach it. Ultimately though they might reflect on what they could have achieved if they had gone for crosses earlier in the game.
Mount proves his all-around worth
Perhaps Mount is cursed to forever have to explain his presence in sides that contain numerous more glamorous alternatives. For Chelsea it was Kai Havertz, left on the bench, for England, Jack Grealish chief among numerous midfield rivals. No matter what he achieves with club and country there may yet be those who are convinced that other options are better.
That Mount has proven so popular with Gareth Southgate and Frank Lampard only adds to the sense that he is a bit of a goody-two-shoes, both managers have in recent weeks felt compelled to deny any sort of favoritism towards the 21-year-old. The latter highlighted a very specific quality that Mount has that will inevitably go underappreciated by a more generalist audience.
"He doesn't do too many treble step overs and flicks over the back of his head as he shouldn't do. He makes really efficient, clean, sharp passes, he presses as well as any midfield player that I've worked with or played alongside," Lampard said.
That pressing was on full display in the build-up to Hudson-Odoi's goal. Mount's lofted pass into his team-mate's stride was the most eye-catching aspect but the opener would never have come about were Chelsea's No.19 not so relentlessly pursuing Doku to win the ball back.
That is more typical of Mount than might otherwise be appreciated. By the time he was withdrawn in the 66th minute no-one bettered his tally of three tackles, matched only by Jorginho and Cesar Azpilicueta, and you suspected few others on the pitch had pressed so diligently.
Mount has been and will continue to be compared with creative midfielders, somewhat inevitably when his presence often means a Grealish or a big-money Chelsea forward will miss out. But when those comparisons are made it is only fair to note the extras that this youngster brings beyond playmaking.
Callum Hudson-Odoi: With such depth to Lampard's attacking options Hudson-Odoi can ill afford to waste those opportunities that came his way. He certainly did not, taking his goal excellently and continually looking to attack the space between full-back and central defender. RATING: 7
Gerzinio Nyamsi: The 6ft 5in defender was more than just a man mountain for crosses in attack and defense. The 23-year-old defended with elegance and composure throughout and was among those who could feel most hard done by in defeat after Giroud managed to get the run on him when Gomis parried Werner's effort upwards. RATING: 8
Ben Chilwell: Loose in possession, this was an atypically careless display from the England left-back. RATING: 4
Chelsea face Tottenham at Stamford Bridge on Sunday before travelling to Sevilla where victory would secure top spot in Group E. Rennes will look to end their recent difficulties in a trip to Strasbourg before facing off against Krasnodar in what could be a de facto playoff for third spot and Europa League qualification.