John Barclay has been denied the chance to end his Scarlets career with a Pro14 final appearance, after rupturing his Achilles.
The Pro14 semi-final line-up is complete, with Scarlets to play Glasgow Warriors, while Munster take on Leinster.
Rory Best scored two tries but Ulster's bid to overtake Edinburgh came to an end with a 24-24 draw away to Munster.
Richard Cockerill says he is excited by what the future holds for Edinburgh after agreeing a new deal until 2021.
Leinster were unable to seal a home semi-final as Benetton Treviso consigned them to a shock home defeat in the Pro14.
Scotland fly-half Duncan Weir has become Worcester Warriors' 10th signing for next season after agreeing terms on a one-year deal.
Edinburgh were beaten at home by Ulster in the Pro14, while the Ospreys thumped Connacht in Swansea.
The semi-final line-up in the European Challenge Cup is complete, after Gloucester and Cardiff Blues reached the last four on Saturday.
There were wins for Glasgow Warriors, Edinburgh and Cheetahs in Pro14 on Saturday, with Duncan Weir among the star performers.
Edinburgh and Cardiff Blues both claimed wins to boost their respective playoff hopes in the Pro14 on Friday.
Rob Harley's record 178th appearance for Glasgow Warriors was one to forget as they were beaten by Munster.
Two years after leaving for Gloucester, Matt Scott is to return to Pro14 with hometown club Edinburgh.