@4everchan is referencing how Berulava and coaches treated Karina Safina, who was Berulava's former partner. Safina was gorgeous, sweet, and very balletic. She had injuries, likely from Berulava dropping her in training, the poor way he partners! In any case, Safina was injured and she always seemed to be in tears, with their coach and Berulava showing aggression, disdain, and negativity toward her.
If you are referencing Chelsea Liu as Danny's former partner prior to Ellie, the concussion Chelsea suffered was due to an absolutely freak accident during a lift dismount in competition. It might have been a divot in the ice catching a toepick. And unfortunately, the backward upside-down angle of the dismount led to Chelsea hitting her head. Danny was also slightly injured. They both had to follow concussion protocols. Chelsea had endured prior concussions, and she had the brunt of it. They ended up splitting and Chelsea took time off prior to coming back with Balasz Nagy, then another split, and now she's in a renewed and joyful partnership with Ryan Bedard.
Falls, concussions, and crashes during warm-ups can and have happened in pairs skating. Ashley & Timothy at Golden Spin comes to mind. But Ash got up and finished the program, despite being unconscious for seconds.
FYI-- Danny O'Shea is not only a great pairs skater, he's a former U.S. Nationals junior men's champion! Danny is the sweetest, kindest, and most loyal of pairs guys. He truly cares about his partners. Ellie & Danny are a match that was heaven-sent! Praises be to the Skate Gods!