In contrast Racing were forced to dig in their heels against Clermont-Auvergne before edging the low-scoring French derby 13-9. Marc Andreu scored a break-away try against the run of play but victory owed more to Racing's defence while head coach Laurent Travers will want to see an improvement on his team's discpline after they were twice reduced to 14 men.
Scarlets head coach Simon Easterby said: "Racing were pretty dogged without the ball against Clermont, which means we have to be accurate because Racing defend very well and haven't conceded many tries this season.
"Their scrum and driving line-out is a weapon for them and while our scrum has been good this season, this will be the toughest test yet.
"They are a pretty effective outfit, have coaches who won the French Championship with Castres last season, and they are starting to look like they are gelling a bit. What we have to do is focus on ourselves, get what we did last weekend in place and then try and counter some of their threats.
"We are going to have to muscle up again against a pretty physical team who with a player like Jonny Sexton in their ranks can play a couple of different games. We know last weekend won't mean anything if we don't perform this weekend against Racing."
Wales outside half Rhys Priestland will go head to head with Irish counterpart Johnny Sexton though injury has prevented a clash between British & Irish Lions centre Jonathan Davies and Jamie Roberts, who is out with an ankle injury.
- Racing beat domestic rivals Clermont last weekend despite having the least amount of time in possession of any team in Round 1 (9 minutes).
- Scarlets have won five of their last seven home matches against French clubs in the Heineken Cup; both of the defeats were against Clermont.
- Racing have won three of nine away games in the Heineken Cup, conceding an average of 28 points per game in these nine matches.
- Only Racing (42) made fewer passes than Scarlets (78) in the first round of action.
- Aaron Shingler's performance against Harlequins earned him a place in the Amlin Opta Index team of the week. The Wales international made a try assist, won six lineouts, made two clean breaks and beat three defenders at the Twickenham Stoop.
- Despite a brilliant try, Jordan Williams missed five tackles in Round 1 - no player missed more during the first weekend of matches in the Heineken Cup.
- Scarlets hooker, Emyr Phillips, hit the target with all 10 of his lineout throws against Harlequins.
- Racing made fewer carries (45) and more tackles (161) than any other side in the opening round of the tournament.
- Both sides were shown two yellow cards apiece last weekend, a joint-high for the round.
- Racing meet a Welsh club in this tournament for the third time. They have lost the previous two (both v Cardiff Blues in 2011/12).