Olivier Giroud spared Chelsea’s blushes to show exactly why he cannot be allowed to leave Stamford Bridge.
The Blues led through Callum Hudson-Odoi but looked like they had blown their big chance to qualify for the knockout phase when Serhou Guirassy equalised.
That all changed when supersub Giroud rose highest to head a stoppage-time winner and fire his team through.
The former Arsenal star’s future is once again up in the air despite Frank Lampard insisting he wants the Frenchman to stay.
Giroud has yet to start a single match in the Premier League or Champions League this season and has only scored twice.
But he is such a good option for Chelsea off the bench, and such a good influence in the dressing room, that the Blues would be mad to let him go.
The Blues swept Rennes aside 3-0 at Stamford Bridge but they were playing against ten men for much of that game after Dalbert was harshly sent off for handball.
This was a different test, but it was Werner again who proved the danger man and he should have scored inside five minutes.
Instead, he ballooned a brilliant but bobbling cross from Callum Haudson-Odoi way over the crossbar from just six yards.
Hudson-Odoi was one of four four changes made by Lampard from the side which beat Newcastle at the weekend.
And the 20-year-old fired Chelsea in front with a composed finish after some great work from Mason Mount.
The Blues midfielder won the ball deep in his own half from Jeremy Doku and sprayed a wonderful crossfield pass right into Hudson-Odoi’s path.
Only a fine reaction save from Alfred Gomis then denied Mount a close-range second for the Blues after Ben Chilwell picked him out with the cross.
But as so often for Chelsea this season, Lampard’s side switched off after that, drifting dangerously through a difficult 20-minute spell.
Rennes could have equalised when Doku got clear down the right and Kurt Zouma blocked…