Owen Williams suffered a hamstring injury while warming up ahead of Wales' Six Nations defeat to Ireland on Saturday.
Exeter Chiefs rallied in the second half against Sale Sharks, but the Premiership leaders still slipped to a first defeat since November.
At the end of another week of crisis, Saracens had rare cause for cheer as they reached the quarter-finals of the European Champions Cup.
Rhys Carre's early red card made life difficult for Saracens, but they still defeated Ospreys in the European Champions Cup.
Five tries in each half saw Premiership basement side Saracens make light work of thumping Worcester Warriors on Saturday.
Munster put in a monumental effort, but Leinster's defence refused to buckle at Thomond Park.
Northampton Saints defeated Gloucester in a barnstorming contest at Franklin's Gardens, while Sale Sharks overcame Bath in the Premiership.
Five tries from the 60th minute onwards gave Gloucester just their second win in eight matches in all competitions.
Brothers Billy and Mako Vunipola played starring roles as reigning champions Saracens defeated Munster in the European Champions Cup.
Rob Baxter's Exeter Chiefs survived a late scare to defeat Sale Sharks and remain firmly on track for the Champions Cup quarter-finals.
London Irish battled to claim a draw at Bristol Bears despite seeing Ollie Hoskins sent off on the stroke of half-time.
La Rochelle's Pierre Bourgarit learned his fate on Wednesday after being sent off for eye-gouging Sale Sharks' Tom Curry.
Sale Sharks saw off a La Rochelle side who were let down by Pierre Bourgarit, as the English team sealed a first European win... Read more
Scrum-half Joe Simpson scored two first-half tries but Gloucester could not contain Toulouse after the break at Kingsholm.
Taylor Swift proved the unlikely inspiration for beleaguered Premiership champions Saracens as they roared to victory at Gloucester.
A looming points deduction would see Saracens facing a Premiership relegation battle this season, but they defeated Gloucester on Saturday.