Most concerning was lock Michael Fatialofa's neck injury suffered when taking the ball into contact only a minute after he entered play as a substitute for Worcester in their 5-62 loss to Saracens.
Fatialofa played for Southland and Auckland in the Mitre 10 Cup and had three seasons for the Hurricanes in Investec Super Rugby before joining Worcester in 2018.
Worcester's director of rugby Alan Solomons told worcesternews.co.uk, "It [Fatialofa's injury] is a massive concern and I'm worried about it but I haven't had a report from the hospital.
"The medics have taken all precautions and done everything possible."
Former All Black Charles Piutau had to be assisted from the field in the last minute in Bristol's 18-31 loss to Leicester.
When looking to step off his left foot the fullback was tackled high by Jonny May and his right knee crumbled beneath him. May also fell on top of him. A penalty was awarded for the high tackle.
Bristol coach Pat Lam told media after the game, "It is not looking great. That makes it doubly worse today because we were into the last minute of play. It is his knee and he has [also] broken his nose [in the same incident]. It doesn't look good for a few weeks now."
Adding to the bad news for Bristol was that another former All Black, prop John Afoa, suffered a rib injury in the 15th minute and had to be replaced.
"In a maul he got pinged in the ribs. It will get scanned to see if it is cartilage damage or a fracture," Lam said.
Whatever the diagnosis, he and Piutau looked set for a spell on the sideline.
The loss was a blow for Bristol in the Premiership while Leicester eased their relegation concerns at the bottom of the competition ladder.
Former Hurricanes utility Jason Woodward made his first appearance for Gloucester since mid-November by getting on the try-scoring sheet in their 29-15 win over Bath.
In the PRO14 competition, Dave Rennie's injury-affected Glasgow side scored a 38-19 win away to Benetton to have a 5-5 record in the competition.
"It was a great performance from a lot of young men, and getting five points over here is not an easy thing to do," Rennie said.