Saracens director of rugby McCall believes that Ashton's decision to depart was likely down to his exile from the Red Rose fold, having failed to add to his 39 caps since his last outing in the summer of 2014.
"In our opinion the best place for him to be as a rugby player is here but obviously he doesn't believe that," McCall told BBC Sport. "Chris made the decision for him and his family that he was going to call time on his time at Saracens and seek a new challenge.
"It's disappointing for us but we will move on quickly from that. Chris has done a great job for this club over four-and-a-half seasons and hopefully he can be part of something good again this year. We fully expect him to make a big contribution this season as well."
Ashton is due to return to action in December after being punished for biting Northampton Saints' Alex Waller - the latest in a long list of disciplinary issues.