In this season of all seasons, depth of talent is going to prove key for any club with real trophy ambitions.
It might not suit Giroud – or his agent – to spend the majority of his time on the bench, but for Lampard, he’s a priceless asset.
His injury time header was as perfectly timed as it was placed.
He makes it look simple – but it was anything but.
The 34-year-old had only been on the pitch for about 20 minutes – but he was sharp enough to be in position to capitalise on Timo Werner’s failure to convert Hakim Ziyech’s through-ball. He also had the technique to make perfect contact and send his header looping into the roof of the net.
Giroud bailed Chelsea out just as they looked like making harder work of Champions League group they’d cruised through up to this point.
Serhou Guirassy’s 85th-minute header cancelled out Callum Hudson-Odoi’s brilliant opener – and looked set to ensure they would have to wait at least one more game to ensure safe passage to the last 16.
But Giroud did what Lampard knows he can – and provided the decisive moment with the type of clinical finish that has evaded Werner in recent games.
In that moment he underlined his value to this team. Lampard will have to hope the promise of more moments like that – and the potential to win major trophies – will convince him to put off thoughts of a January move.
Chelsea were not at their best, but this was another game in which their credentials were underlined.
They got the job done on a night when the full depth of quality at Lampard’s disposal was showcased.
On a rare start, Hudson-Odoi provided a reminder of why Bayern Munich were so desperate to lure him away from Stamford Bridge.
Ziyech emerged from the bench to create the move that led to the winner and another golden opportunity for Ben Chilwell.
N’Golo Kante and Reece James were other substitutes, while Christian Pulisic stayed back in London to try to get fit for Sunday’s clash with Tottenham.
And there was Giroud – third in the pecking order of Chelsea’s strikers – but with the calibre to settle a game like this.
Victory saw Chelsea win three straight Champions League games for the first time since 2015, which underlines how their fortunes in the competition have fared in recent years.
It was also the first time they have secured qualification this early in nine years.
They are statistics to make Giroud believe he can part of something special this season.
Safe progress now means Lampard can concentrate on the hectic Premier League schedule coming up over the next month – which starts with Sunday’s top of the table showdown with Spurs.
Chelsea could and should have had the game wrapped up by midway through the first half.
Werner was guilty of wasting a golden opportunity when failing to keep down his shot after Hudson-Odoi’s ball.
Then a real moment of quality gave Chelsea the lead, with Mason Mount pivotal to it.
The midfielder first won the ball deep in his own half before driving forward. He then looked up to sweep a pass into the path of Hudson-Odoi, who slid his finish past the advancing Alfred Gomis.
And when Mount poked Ben Chilwell’s pullback goal-wards, it took a smart save from Gomis to deny him.
Chelsea’s intensity dropped and they were eventually made to pay when Guirassy was left unmarked to head past Edouard Mendy.
It felt like a sucker punch until Giroud provided the knockout.
Mount demonstrates his quality
Setting Hudson-Odoi to put Chelsea in front, Mount underlined the side of his game that seems to be overlooked during the debate over whether he’s worth his place.
So much of the discussion around him is based on his work rate and economical use of the ball. But he has the ability to open up defences with his vision and technique.
That he won the ball deep in his own half before spraying a pass into the path of Hudson-Odoi just showcased his all-round quality.
Tottenham on Lampard’s mind
Lampard made all the right noises beforehand – warning his players not to take Rennes lightly or be distracted by Sunday’s showdown with Spurs – it was clear he had one eye on that top of the table clash.
His team to face Jose Mourinho’s men is likely to look markedly different from his starting XI in France.
Ziyech, Kante and James will almost certainly come straight back in, while Kai Havertz could push for his first start since before the international break.
That Chelsea could replace those names with the quality of Hudon-Odoi and Jorginho is a measure of the strength in depth at Lampard’s disposal.