But it is her outspoken nature off the pitch that has arguably accelerated her rise to global prominence.
A vocal supporter of women’s rights and equal pay – as well as taking on US president Donald Trump in a Twitter spat - Rapinoe has become an icon for many around the world.
Former US midfielder Lilly, who holds the record for most international appearances by a male or female footballer with 352, was impressed with the way Rapinoe and her team-mates conducted themselves during the World Cup in France over the summer as well as their general outlook.
Asked about Rapinoe's influence, Lilly told Omnisport: "They have a platform, they are fighting for women’s sport, women’s football to make it a better environment and it’s being heard.
"It’s helping other countries to recognise that the investment is needed.
"The US team did a great job, the last World Cup was pretty phenomenal for what they accomplished. I’m proud of what they continue to fight for."
The World Cup in France elevated the profile of women’s football to new levels and Lilly is hopeful that momentum will continue.
She added: "There’s no other way to go. The investment that FIFA is putting behind the women’s game is the catalyst for it because of the recognition of where we are and where we need to go.
"The more teams we create, build that base up for competition, the better the World Cup will be.
"They are going to expand to 32 teams so we will need those teams to have some finance behind them. I see great things for the future of the women’s game. We have to keep backing it."