Mercer has been ineligible for his country since heading abroad to the Top 14 in 2021 and won the last of his two Test appearance while at Bath four years ago.
The back-rower capped a superb season by being named the Top 14's player of the year after winning the league in June.
"For me, I want to challenge for World Cup selection," Mercer told reporters.
"It's always going to sit in the back of my mind.
"I'm ready to go back to England and put my name in the mix," he added after the glamorous ceremony held in Paris.
He featured in all but two of his club's league fixtures, scoring twice, to become the first English winner of the award which started in 2004.
Toulouse scrum-half Antoine Dupont, who won last year's prize, and his France team-mate No. 8 Greg Alldritt, who lifted the European Champions Cup with La Rochelle, were also on the shortlist.
Dupont was named best international player, after helping France to their first Six Nations Grand Slam since 2010 in March and an impressive victory over New Zealand in November.
"To rub shoulders with Alldritt and Dupont I could have gone home happy," Mercer said.
"To win it tops off a great year for me, it's pretty surreal right now," he added.
This weekend, Mercer's side host record 21-time champions Toulouse in the fifth round of the season after starting the campaign with three wins from four games.
"It's a really tough league, it's a marathon you enjoy rather than slogging it out," Mercer said.
"We're four games into the new season, it's going to be another slog again but I'm looking forward to it."
