This weekend's hosts recently suffered their third defeat on the bounce with a 1-0 loss to Bordeaux on Friday, whereas Chelsea stormed to their fifth win in a row over Newcastle United.
Having started the season with so much promise and a genuine sense of belief that Rennes could forge a title challenge in Ligue 1, Julien Stephan's men are now enduring a period of capitulation amid an unforgiving fixture schedule.
The eight-game unbeaten run that Rennes managed to string together at the start of the season is firmly in the past as Les Rouge et Noir have now tasted defeat in five of their last six matches in all competitions, including a 1-0 home loss to Bordeaux on Friday.
The veteran Hatem Ben Arfa notched up the only goal in that game as Rennes' alarming slump continued, with their only victory in their last eight coming against Brest, and even then Stephan's men only just scraped a 2-1 triumph on their own turf.
The Ligue 1 outfit have hardly fared better in their first-ever Champions League venture either, as Rennes already sit bottom of the pile having taken just one point from a possible nine at this midway stage - with Russian side Krasnodar ahead of Stephan's men courtesy of head-to-head away goals scored.
Should Rennes lose to Chelsea and Sevilla overcome Krasnodar this week, Les Rouge et Noir's hopes of making the knockout stages will be dashed, and the best that Stephan's men could hope for after that would be a spot in the Europa League if they manage to pip Krasnodar to third place.
In stark contrast, Chelsea cannot stop winning at the moment, with Frank Lampard finally witnessing his talented attacking crop combining to great effect.
The Blues will endeavour to win their sixth game in a row in all competitions when they cross the channel in midweek, and while Chelsea experienced moments of uncertainty against Newcastle United, Lampard's side eventually ran out comfortable winners in the North East.
A Federico Fernandez own goal set the tone for the game early on, with Karl Darlow forced into a couple of fine saves to keep the scoreline at 1-0, but the Magpies shot-stopper was powerless to stop Tammy Abraham doubling Chelsea's lead in the second half after a brilliant solo run from Timo Werner.
That result saw Chelsea lead the way in the Premier League before Tottenham Hotspur overcame Manchester City a few hours later, but one table that Lampard's men still top is Champions League Group E, with Chelsea ahead of Sevilla on goal difference having drawn 0-0 with the Spaniards already.
With seven goals scored and zero conceded so far in Europe, Chelsea's qualification for the knockout stages will be confirmed so long as they beat Rennes and Krasnodar fail to get the better of Sevilla this week.
Chelsea's showdown with Rennes at Stamford Bridge saw the Blues run out 3-0 winners earlier in November, with two Werner penalties putting Chelsea in control before half time, while Abraham also got in on the act in the second 45.
Rennes Champions League form: DLL
Rennes form (all competitions): LLWLLL
Chelsea Champions League form: DWW
Chelsea form (all competitions): DWWWWW
After being sent off in controversial circumstances against Chelsea earlier in the month, Dalbert will play no part for Rennes, but the left-back was not involved in any capacity against Bordeaux either.
However, the game will come too soon for the injured Christian Pulisic, who continues to nurse a hamstring problem, but Lampard otherwise has a fully-fit squad at his disposal.
Werner may be given a much-needed rest for this one as Callum Hudson-Odoi looks to impress, and Cesar Azpilicueta is in contention for a start at right-back after Reece James suffered a small injury against Newcastle, although the England international still completed the full 90 minutes.
Rennes possible starting lineup:
Gomis; Traore, Aguerd, Da Silva, Truffert; Nzonzi, Camavinga, Bourigeaud; Doku, Guirassy, Terrier
Chelsea possible starting lineup:
Mendy; Azpilicueta, Zouma, Silva, Chilwell; Kante, Jorginho, Mount; Ziyech, Abraham, Hudson-Odoi
We say: Rennes 0-2 Chelsea
Chelsea's defence is one of only two in the Champions League yet to be breached in the group stage - the other being Liverpool's - and Lampard should have confidence in his rearguard to keep yet another clean sheet here. Rennes are in a rut at the moment and have been performing abysmally compared to a Chelsea side sweeping aside all who stand before them, and we expect the Blues to triumph with ease and see their qualification for the knockout stages confirmed in midweek.