But there 's an essential toughness to her , an attitude that formed on those courts and persists to this day .
Serena 's since had so many coaches that it 's impossible for Pyles to spot the fruits of his teaching in her game .
There 's an essential toughness to Serena , an attitude that formed on those courts and persists to this day .
Serena 's since had so many coaches that it 's impossible for Pyles to spot the fruits of his teaching in her game .