His seasonal bow had been postponed due to a quad muscle injury, which he sustained when warming up prior to the league game against the Cardiff Blues last month.
Looking forward to the start of the Heineken Cup campaign, Sexton said: "It's a very tough pool. I think the two toughest pools will be ours and Munster's, so to get out of them and into the knockout stages will be an achievement in itself.
"If we can get out of our pool, we have got every chance of going on to win the competition.
"But we're not getting ahead of ourselves. The first target is to get out of the pool and that's going to be pretty tough."
Asked if he will be fit to line out against Racing this weekend, he admitted: "I hope so. It's obviously been a frustrating few weeks with injury, more so because I was fit for every session in pre-season and then 20 minutes before my first game I pulled up with a slight quad injury.
"Then I made it worse by trying to come back a bit early. So lesson learned.
"I overkicked a little bit, just being anxious to get the season off to a good start and paid the price. I went into the Cardiff warm-up and then pulled up, it was more precaution at the time that I didn't play but I made it a little bit worse by coming too early for the next game and then the game after that."
Experienced flanker Shane Jennings will also be available for selection and aside from the usual bumps and bruises, there are no other injury concerns for Leinster ahead of the visit of the Top 14 leaders.
A decision on the availability of captain Leo Cullen will be made at Thursday's team announcement. The lock has been sidelined with a shoulder injury for the opening weeks of the season.
Over 15,500 tickets have been sold for Saturday's game and tickets are still available (priced €10 to €60) from here, from Spar (Donnybrook) and the Leinster Rugby Store (Donnybrook).