Dan Lydiate has withdrawn from the starting team for tonight's Champions Cup clash with Saracens at Allianz Park and is replaced by Guy Mercer.
The flanker starts his first European game for the Ospreys having arrived at the Liberty Stadium in the summer, after Lydiate pulled out with a back problem.
Mercer's place on the bench is taken by Sam Cross, the Wales and GB sevens star in line for his competitive debut for the region if he gets on.
