Merrin defended the club's decisions to let both Cartwright and Matt Moylan go over the summer break, indicating they were not on the same page with the rest of the squad.
Cartwright's exit at the Panthers was considered months in the making, and Merrin said modern day rugby league players were professional enough to adjust to sudden departures and arrivals regardless of when it occurs.
"Within the playing group there is a lot of clarity there," Merrin said ahead of the club's trial with the Sydney Roosters on Saturday night.