Saracens left to sweat on Farrell's fitness
Owen Farrell faces a race against time to be fit for Saracens clash with Leinster on Sunday after Billy Vunipola appeared to lose his fight to play.
The England three-quarter, nursing a quad injury, watched from the sidelines at the London Stadium on Saturday as Mark McCall's team secured a tortuous 24-11 win over Aviva Premiership rivals Harlequins in a desperately stop-start affair which saw Maro Itoje return to form after a difficult Six Nations campaign.
Farrell missed the match along with England lock George Kruis (back) and No8 Vunipola - who has been out of action since breaking his arm in January - and the Saracens fly half remains a doubt for Sunday's hugely-anticipated encounter in Dublin.
With captain and inside centre Brad Barritt also struggling after appearing to leave the field with concussion in the second half against Quins, 24-year-old Alex Lozowski could be a pivotal play-maker at the Aviva Stadium.
Lozowski, capped four times by England, produced an excellent all-round performance in a largely disjointed win over hapless Quins and insists he is ready if called upon.
"I will do whatever the team needs, whether that is starting or coming off the bench. I am looking forward to making a difference. " Losowski said.
McCall said: "Owen has got a quad injury. George Kruis has a back injury. Both are touch and go for next week. I don't think Billy will make it."