Leinster are taking a wait-and-see approach on a number of frontline players ahead of Saturday's Champions Cup semi-final against Scarlets at Aviva Stadium (kick-off 3.30pm).

Senior coach Stuart Lancaster said they "are not giving up hope" on Sean O'Brien making it, with doubts around Luke McGrath's availability also a worry.

However Robbie Henshaw has "ticked all the boxes" and is ready to go for the Lansdowne Road showdown.

Ireland centre Henshaw is back in full training following the shoulder injury he suffered scoring a try during the Six Nations triumph over Italy. In another boost, Jack Conan returns to training this week  after a spell out with a knee injury.

O'Brien's latest comeback lasted just 40 minutes as he was withdrawn at half-time of Saturday's home defeat to Treviso and his shoulder will be assessed later in the week as Leo Cullen's men prepare for their third European semi-final in five seasons.

"We're not giving up hope on Sean," Lancaster said on Monday.

"There comes a point in the week where you need to make a decision for the cohesion of the team. We're not quite at that moment yet.

"Today and tomorrow morning's training will be key to that. Robbie is good to go. He's ticked all the boxes that he needs to tick."

Arguably of more concern to the province than O'Brien - who operates in Leinster's impressively stocked back-row - is the ankle injury that McGrath is nursing.

The scrum-half has not played since the quarter-final win over Saracens and, should he miss out, Leinster will bring in Jamison Gibson-Park at 9. 

"(McGrath) is in a similar situation to Sean I would think," Lancaster added. "He's on an upward curve but again, the clock is ticking on that one."

Gibson-Park's inclusion, along with Scott Fardy in the second-row, would see the exciting James Lowe miss out on the matchday squad due to a limit on the number of southern hemisphere players who can be involved.

The backline could easier absorb that loss if Jordan Larmour is fit and well, with Leinster today reporting the Irish wing came through the Treviso test unscathed.

Hooker Richardt Strauss misses out due to a calf injury sustained against the Italians, while Rhys Ruddock is also a likely absentee due to a hamstring problem.

Follow Leinster v Scarlets via our live blog on RTÉ.ie and the News Now App (kick-off 3.30pm), or hear live updates on RTÉ Radio 1's Saturday Sport. Follow Racing 92 v Munster (kick-off 3.15pm) via our live blog or listen to live and exclusive radio commentary on RTÉ Radio 1's Sunday Sport.